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"Standard parts" for rf amps?
Hi all -
I'm not new to electronics but to vhf comm. I want to build small circuits: LNA, power amp to 10 watts, etc. At the moment between 10MegHz and 150MegHz. What are the standard parts, cheap but effective, preferable with spice model availability (I'm doing much with LTspice)? Transistors, ICs, coil-suppliers, suppliers in general for small quantities Please no triodes etc. I like more SMD ;-) Lists somewhere in the net? Japanese parts? I think such lists will be of interest to others too! Thank you!! Best regards - Henry |
"Standard parts" for rf amps?
You are going to use Spice to model an RF circuit. DId I get that right?
Jim "Henry Kiefer" wrote in message ... Hi all - I'm not new to electronics but to vhf comm. I want to build small circuits: LNA, power amp to 10 watts, etc. At the moment between 10MegHz and 150MegHz. What are the standard parts, cheap but effective, preferable with spice model availability (I'm doing much with LTspice)? Transistors, ICs, coil-suppliers, suppliers in general for small quantities |
"Standard parts" for rf amps?
Yes Jim!
Im not very experienced there (Digital designs/layout is my profession) - but for example I designed a LNA and got simulations results (even for noise performance) very similar to a real circuit built from a ham with great background (found later on the net). Even a Synchronous Oscillator for 145MegHz seem to work with LTspice. I work on it today trying to modify it to an fsk modulated power oscillator to keep component count to the lowest. Why you ask? - Henry "RST Engineering (jw)" schrieb im Newsbeitrag ... You are going to use Spice to model an RF circuit. DId I get that right? Jim "Henry Kiefer" wrote in message ... Hi all - I'm not new to electronics but to vhf comm. I want to build small circuits: LNA, power amp to 10 watts, etc. At the moment between 10MegHz and 150MegHz. What are the standard parts, cheap but effective, preferable with spice model availability (I'm doing much with LTspice)? Transistors, ICs, coil-suppliers, suppliers in general for small quantities |
"Standard parts" for rf amps?
No list needed!
VHF traditionally begins at around 6 meters, but design techniques there are not much different from those used at 10 meters. The point where you need to begin being more careful regarding circuit layout is around 2 meters. Many devices that operate on the lower shortwave bands still function reasonably well at this region. So... the same analog circuits will work, but WATCH OUT for circuit layout. The Eternal Squire |
"Standard parts" for rf amps?
there are lots of parts...
stat by looking at these vendors Mini Circuits Maxum Mark |
"Standard parts" for rf amps?
"Henry Kiefer" wrote in message
... Hi all - I'm not new to electronics but to vhf comm. I want to build small circuits: LNA, power amp to 10 watts, etc. At the moment between 10MegHz and 150MegHz. What are the standard parts, cheap but effective, preferable with spice model availability (I'm doing much with LTspice)? Transistors, ICs, coil-suppliers, suppliers in general for small quantities Please no triodes etc. I like more SMD ;-) Lists somewhere in the net? Japanese parts? I think such lists will be of interest to others too! Thank you!! Best regards - Henry http://www.rfparts.com/ is a good source of RF components. Also look at http://www.danssmallpartsandkits.net/ for great prices on common parts. -- Dave M MasonDG44 at comcast dot net (Just substitute the appropriate characters in the address) Never take a laxative and a sleeping pill at the same time!! |
"Standard parts" for rf amps?
On Mon, 21 Nov 2005 16:40:40 -0800, "RST Engineering \(jw\)"
wrote: You are going to use Spice to model an RF circuit. DId I get that right? Jim Why not? John |
"Standard parts" for rf amps?
Well, just for starters, what does Spice say about a 1000 pf capacitor with
either ½" lead lengths or a total of 1" of PCB trace at 150 MHz.? Jim "John Larkin" wrote in message ... On Mon, 21 Nov 2005 16:40:40 -0800, "RST Engineering \(jw\)" wrote: You are going to use Spice to model an RF circuit. DId I get that right? Jim Why not? John |
"Standard parts" for rf amps?
Ok Jim. You're asked about the stray components hidden in the real
parts/circuit. If you take the values from the datasheets for die and/or package or give it a guess if not available, and add values for the pcb lines, you have a good simulation result. The pcb by itself is not of much interest if you simulate not much over 100MegHz. Even starting a oscillator with thermal noise is possible! Sure, you must know what you're doing :-) Spice by itself can simulate almost all if you have the right models included - even if you wanna simulate a mechanical system. There is no frequency limit at least to 100GHz. Do you had bad result doing Spice? To come back to your question: Spice will give you better results than your real circuit! You can connect a probe with no interaction to the circuit! Try this with your real parts! Don't forget the component variations in real circuits coming from the manufacturing processes of the parts. - Henry "RST Engineering" schrieb im Newsbeitrag ... Well, just for starters, what does Spice say about a 1000 pf capacitor with either ½" lead lengths or a total of 1" of PCB trace at 150 MHz.? Jim "John Larkin" wrote in message ... On Mon, 21 Nov 2005 16:40:40 -0800, "RST Engineering \(jw\)" wrote: You are going to use Spice to model an RF circuit. DId I get that right? Jim Why not? John |
"Standard parts" for rf amps?
Thank Mark!
MC and Maxim is not new to me. I thought on list of cheap, easy getting parts with reasonable performance. - Henry "Mark" schrieb im Newsbeitrag oups.com... there are lots of parts... stat by looking at these vendors Mini Circuits Maxum Mark |
"Standard parts" for rf amps?
On Tue, 22 Nov 2005 12:20:25 +0100, "Henry Kiefer"
wrote: Thank Mark! MC and Maxim is not new to me. I thought on list of cheap, easy getting parts with reasonable performance. - Henry Minicircuits the MIMICs and mixers are of most interest and there are inexpensive versions in the line up. What both offer is well characterized RF 50 ohm port parts that behave well in circuits. For example you can build a DBM, can you say for sure what the characteristics will be from say 2-500mhz? Other useful parts from there are VCOs and RF transformers. Allison |
"Standard parts" for rf amps?
"Henry Kiefer" wrote in message ... Ok Jim. You're asked about the stray components hidden in the real parts/circuit. There is nothing hidden at all. Strays are a part of the real life at VHF and above. Sometimes strays have more effect than the part itself. If you take the values from the datasheets for die and/or package or give it a guess if not available, and add values for the pcb lines, you have a good simulation result. Horsefeathers. What "values" do you add for the pcb lines? The pcb by itself is not of much interest if you simulate not much over 100MegHz. Even starting a oscillator with thermal noise is possible! Sure, you must know what you're doing :-) As with anything in the world. Spice by itself can simulate almost all if you have the right models included - even if you wanna simulate a mechanical system. There is no frequency limit at least to 100GHz. The problem is getting the right models, which is an art in and of itself. Do you had bad result doing Spice? To come back to your question: Spice will give you better results than your real circuit! You can connect a probe with no interaction to the circuit! Try this with your real parts! Don't forget the component variations in real circuits coming from the manufacturing processes of the parts. Again I ask the question: What does Spice say about a 1000 pf capacitor with 1" total lead length at 150 MHz.? Don't give me the BS about Spice being "better than a real circuit". Until you can give me a ferrite slug on one end of a toothpick and a brass slug on the other end to increase or decrease inductance in Spice, the physical circuit is the "real" circuit. Jim |
"Standard parts" for rf amps?
RST Engineering wrote:
"Henry Kiefer" wrote in message ... Ok Jim. You're asked about the stray components hidden in the real parts/circuit. There is nothing hidden at all. Strays are a part of the real life at VHF and above. Sometimes strays have more effect than the part itself. You have to put the strays into the spice model if you want an accurate result, just like you would have to if you work it out with a pencil and paper. If you take the values from the datasheets for die and/or package or give it a guess if not available, and add values for the pcb lines, you have a good simulation result. Horsefeathers. What "values" do you add for the pcb lines? You can work out the inductance, resistance (including skin effect) and capacitance of arbitrary structures using the free programs FastCap and FastHenry, though these consider inductive and capacitive effects separately so you have to break the problem into several parts sometimes, e.g. if the structure is a significant fraction of a wavelength in size. Constructing the model files can be tedious, and you may end up having to write some code to automate it. You can view the model files using a viewer program which used to be and hopefully still is available from www.fastfieldsolvers.com You could also buy one of the commercial full-wave solvers if you have more spare money than time. The pcb by itself is not of much interest if you simulate not much over 100MegHz. Even starting a oscillator with thermal noise is possible! Sure, you must know what you're doing :-) As with anything in the world. Spice by itself can simulate almost all if you have the right models included - even if you wanna simulate a mechanical system. There is no frequency limit at least to 100GHz. The problem is getting the right models, which is an art in and of itself. Right but you have to do that one way or another anyway even if the model is inside your head, unless you design purely by trial and error. Do you had bad result doing Spice? To come back to your question: Spice will give you better results than your real circuit! You can connect a probe with no interaction to the circuit! Try this with your real parts! Don't forget the component variations in real circuits coming from the manufacturing processes of the parts. Again I ask the question: What does Spice say about a 1000 pf capacitor with 1" total lead length at 150 MHz.? Don't give me the BS about Spice being "better than a real circuit". Until you can give me a ferrite slug on one end of a toothpick and a brass slug on the other end to increase or decrease inductance in Spice, the physical circuit is the "real" circuit. Jim The real advantage of spice is in situations where trial and error is more expensive than getting it right the first time (where you can justify spending a long time making good models). He does also have a point about being able to probe components inside a circuit that you could never probe on a real one due to loading effects of the real probe. It seems to me that your real objection is not with computer simulation of circuits, but rather with poor models for components. Fair enough, garbage in garbage out, but I would consider using bad models to be a form of 'user error'. Chris |
"Standard parts" for rf amps?
In article ,
RST Engineering wrote: "Henry Kiefer" wrote in message ... Ok Jim. You're asked about the stray components hidden in the real parts/circuit. There is nothing hidden at all. Strays are a part of the real life at VHF and above. Sometimes strays have more effect than the part itself. Heck, that can happen before you hit 1MHz. Check out the ESL and ESR of a 47,000uF capacitor some time. -- -- forging knowledge |
"Standard parts" for rf amps?
Ken Smith wrote:
Heck, that can happen before you hit 1MHz. Check out the ESL and ESR of a 47,000uF capacitor some time. How about dielectric absorption ("soak")? I first encountered this in an electrolytic capacitor being used for generating a sweep of about a minute duration. The capacitor had to be kept shorted for several seconds between sweeps in order for the charge to adequately empty, an equivalent frequency of less than one Hz. Roy Lewallen, W7EL |
"Standard parts" for rf amps?
"Ken Smith" wrote in message
... Heck, that can happen before you hit 1MHz. Check out the ESL and ESR of a 47,000uF capacitor some time. For some of the university work I've done, some of our reference papers are from people modeling power lines as full-fledged transmission lines that are many wavelengths long at 50Hz. No simple equivalent circuit model works for them either! |
"Standard parts" for rf amps?
"Joel Kolstad" wrote in message
... For some of the university work I've done, some of our reference papers are from people modeling power lines as full-fledged transmission lines that are many wavelengths long at 50Hz. No simple equivalent circuit model works for them either! OK, I did get a little over-excited there -- it should say "that are significant fractions of a wavelength long," (e.g., more than 1/6th) such that you can't use a simple circuit model for them. |
"Standard parts" for rf amps?
On Mon, 21 Nov 2005 23:55:26 -0800, "RST Engineering"
wrote: Well, just for starters, what does Spice say about a 1000 pf capacitor with either ½" lead lengths or a total of 1" of PCB trace at 150 MHz.? Jim When they matter, just poke in the appropriate series L or a bit of transmission line. I use Spice now and then to sim picosecond stuff. Even if the simulation isn't highly accurate, it helps train your instincts, shows you which parasitics will have which effects, so when you build the real thing you have a jump on the complexity. Hell, 150 MHz is slow. John |
"Standard parts" for rf amps?
On Tue, 22 Nov 2005 10:05:02 -0800, "RST Engineering"
wrote: "Henry Kiefer" wrote in message ... Ok Jim. You're asked about the stray components hidden in the real parts/circuit. There is nothing hidden at all. Strays are a part of the real life at VHF and above. Sometimes strays have more effect than the part itself. If you take the values from the datasheets for die and/or package or give it a guess if not available, and add values for the pcb lines, you have a good simulation result. Horsefeathers. What "values" do you add for the pcb lines? Lumped L and C if things are slow, or a hunk of transmission line when things get fast. Works fine. John |
"Standard parts" for rf amps?
Joel Kolstad wrote:
"Joel Kolstad" wrote in message ... For some of the university work I've done, some of our reference papers are from people modeling power lines as full-fledged transmission lines that are many wavelengths long at 50Hz. No simple equivalent circuit model works for them either! OK, I did get a little over-excited there -- it should say "that are significant fractions of a wavelength long," (e.g., more than 1/6th) such that you can't use a simple circuit model for them. That's interesting -- SPICE has models for (lossless) transmission lines, and lines of that length can also be adequately modeled with a few LC sections. I can imagine line loss could be tricky, though. I've modeled skin effect loss in the process of designing time-domain circuits to compensate for delay line loss over a wide time range (and therefore broad frequency range). But loss due to interaction of the fields with ground underneath the wires might be more difficult. At least you've only got one frequency to deal with -- unless harmonic content is high enough to worry about. Perhaps you've also got to deal with loss due to radiation? Roy Lewallen, W7EL |
"Standard parts" for rf amps?
Agreed, John, 150 MHz is damned near DC for a lot of us, but as yet I have
no answer from the "spice" folks for the 1 nf capacitor question. A lot of fancydancing but no answers. Jim "John Larkin" wrote in message ... On Mon, 21 Nov 2005 23:55:26 -0800, "RST Engineering" wrote: Well, just for starters, what does Spice say about a 1000 pf capacitor with either ½" lead lengths or a total of 1" of PCB trace at 150 MHz.? Jim When they matter, just poke in the appropriate series L or a bit of transmission line. I use Spice now and then to sim picosecond stuff. Even if the simulation isn't highly accurate, it helps train your instincts, shows you which parasitics will have which effects, so when you build the real thing you have a jump on the complexity. Hell, 150 MHz is slow. John |
"Standard parts" for rf amps?
"RST Engineering \(jw\)" writes:
Agreed, John, 150 MHz is damned near DC for a lot of us, but as yet I have no answer from the "spice" folks for the 1 nf capacitor question. A lot of fancydancing but no answers. I am not an expert, but can you not just add a bit of series L to approximate this? Or even transmission line for higher frequencies / longer tracks. I have had surprisingly good results simulating a single transistor UHF oscillator at ~500MHz. The results agreed with reality quite well, even *without* explicitly modelling all the parasitics. Certainly spice was better than me at predicting what would happen (although that is not saying much!) I guess perhaps the reason that I could get away with this was because of the small size and high performance of SMT parts these days. -- John Devereux |
"Standard parts" for rf amps?
jw\ wrote...
Agreed, John, 150 MHz is damned near DC for a lot of us, but as yet I have no answer from the "spice" folks for the 1 nf capacitor question. A lot of fancydancing but no answers. Spice, smice. You got good answers. Wake up, spice is just an engine to run your component models in circuits of your making. Once one gets beyond the "toy" level of using spice it becomes necessary to vet and complete the models of all your critical components, including parasitic circuit elements. Want a good RF capacitor model, you do well to make it yourself, from the manufacturer's data and info, and from your understanding of the part, aided by theory and bench measurements. Then vet your model with more bench measurements. Thinking about component leads and PCB wiring? Hey, you need to explicitly add all these into your circuit. Just don't blame any resulting shortcomings on "spice." -- Thanks, - Win |
"Standard parts" for rf amps?
RST Engineering (jw) wrote:
Agreed, John, 150 MHz is damned near DC for a lot of us, but as yet I have no answer from the "spice" folks for the 1 nf capacitor question. A lot of fancydancing but no answers. Jim I didn't realize that this question was addressed to all "'spice' folks", but was directed only to the OP. That's probably why the "'spice' folks" haven't leapt to respond. Anyone who uses SPICE professionally, and indeed a great number of amateur users should be able to answer the question easily. At 150 MHz, a capacitor lead can generally be handled as a single lumped inductance. The amount depends on the wire's diameter and environment, but around 7 nH is a good working number for a half inch lead. The inductance of the capacitor body itself might have to be included in the model if high accuracy is important. Capacitance to ground, from both the leads and the capacitor body, might also be important if the impedance of the circuit to ground is high. If so, it can be included. The way I'd approach inclusion of the C would be to calculate the impedance and length of the transmission line comprised of the lead and ground plane or capacitor body and ground plane, then convert those values to a single series L and shunt C rather than just directly using a transmission line model -- very short transmission lines in a model can greatly slow SPICE calculations unless there are also other very short time constants involved. On the other hand, if the "leads" are PC traces over a ground plane, shunt capacitance will be higher, and the approach I mentioned with the transmission line is the way I'd always do it. The model for the leads would include both L and C. As an example, if the "lead" is a .010" trace on .032" FR4 material (er ~ 5) over a ground plane, it makes a transmission line of Z0 = 105 ohms, velocity factor 0.55. The equivalent L and C of a half inch of this line are 8 nH and 0.73 pF respectively. Other characteristics of the capacitor such as ESR might have to be included in the model depending on the application. You gave a capacitor value in your question -- an ideal capacitor of that value would of course be the other part of the model. SPICE is used daily, as it has been for decades, by professionals and produces strikingly good results in the hands of someone who is skilled at modeling and has a good understanding of the circuitry being modeled. I've personally used SPICE for modeling linear to highly nonlinear circuits up to 50 GHz, where even tiny SMT components were often modeled as transmission lines and every pad and solder blob is significant and included. The results were used in the design of products which have been successfully produced by the thousands and sold for years. Roy Lewallen, W7EL |
"Standard parts" for rf amps?
On Wed, 23 Nov 2005 06:23:58 -0800, Roy Lewallen
wrote: RST Engineering (jw) wrote: Agreed, John, 150 MHz is damned near DC for a lot of us, but as yet I have no answer from the "spice" folks for the 1 nf capacitor question. A lot of fancydancing but no answers. Jim I didn't realize that this question was addressed to all "'spice' folks", but was directed only to the OP. That's probably why the "'spice' folks" haven't leapt to respond. Anyone who uses SPICE professionally, and indeed a great number of amateur users should be able to answer the question easily. At 150 MHz, a capacitor lead can generally be handled as a single lumped inductance. The amount depends on the wire's diameter and environment, but around 7 nH is a good working number for a half inch lead. The inductance of the capacitor body itself might have to be included in the model if high accuracy is important. Capacitance to ground, from both the leads and the capacitor body, might also be important if the impedance of the circuit to ground is high. If so, it can be included. The way I'd approach inclusion of the C would be to calculate the impedance and length of the transmission line comprised of the lead and ground plane or capacitor body and ground plane, then convert those values to a single series L and shunt C rather than just directly using a transmission line model -- very short transmission lines in a model can greatly slow SPICE calculations unless there are also other very short time constants involved. The problem is the higher the frequency the more second and third order effects are noted. A 1000pF cap at 1mhz is a cap for all intents. At 150mhz it's now a complex RLC. On the other hand, if the "leads" are PC traces over a ground plane, shunt capacitance will be higher, and the approach I mentioned with the transmission line is the way I'd always do it. The model for the leads would include both L and C. As an example, if the "lead" is a .010" trace on .032" FR4 material (er ~ 5) over a ground plane, it makes a transmission line of Z0 = 105 ohms, velocity factor 0.55. The equivalent L and C of a half inch of this line are 8 nH and 0.73 pF respectively. There is a point here where you have to ask is a PCB trace a cap, inductor or more realisticly a transmission line. Each has it's model and they are different. With two sided (or more layers) board the transmission line model is likely the one to use. Especially if your working with VHF transistors at any power level as impedences are in the range of a few hundred ohms on the high side and fractions of an ohm at the low side. Typical 30-100W devices have an imput imedence under 2 ohms ( and Xc) and output in the sub 4 ohms range depending on power. In those cases everything counts and getting hard numbers requires some work. It hits a hard nail on what model to use and when because spice will only give the results you asked for be they real or imagined. Other characteristics of the capacitor such as ESR might have to be included in the model depending on the application. In most I'd naturally assume though at low VHF it's less signigicant than at 2.4ghz. You gave a capacitor value in your question -- an ideal capacitor of that value would of course be the other part of the model. And depending on frequency it may be a open ended transmission line on the etch. SPICE is used daily, as it has been for decades, by professionals and produces strikingly good results in the hands of someone who is skilled at modeling and has a good understanding of the circuitry being modeled. I've personally used SPICE for modeling linear to highly nonlinear circuits up to 50 GHz, where even tiny SMT components were often modeled as transmission lines and every pad and solder blob is significant and included. The results were used in the design of products which have been successfully produced by the thousands and sold for years. Roy Lewallen, W7EL Spice is a great tool. Like every tool one must know how it works, how to use it to its fullest and knowing the tool can hurt you if abused. When introduced to spice for the first time I was told garbage in, garbage out and never assume that computer crunched garbage is anything other than composted garbage. What I've found is that Spice does allow you the luxury of saying "what if" or "how does that affect xxx" even if you are not sure it's real. Allison KB1GMX |
"Standard parts" for rf amps?
I know of a german power line corporation who develops Spice models for
their power line test equipment. So it must be possible... - Henry "Joel Kolstad" schrieb im Newsbeitrag ... "Ken Smith" wrote in message ... Heck, that can happen before you hit 1MHz. Check out the ESL and ESR of a 47,000uF capacitor some time. For some of the university work I've done, some of our reference papers are from people modeling power lines as full-fledged transmission lines that are many wavelengths long at 50Hz. No simple equivalent circuit model works for them either! |
"Standard parts" for rf amps?
I don't know why "RST" is so aggressive but I would mention here, that the
really funny part begins if you garbage in and get meaningful output! I like to smell the solder iron but it can be very interesting playing with Spice and see how changing values can and CAN BE NOT have a drastic result in the simulation. Sometimes changes are not so great in result and parts can be simpler made. e.g. changed from 1% to 5% or more. - Henry schrieb im Newsbeitrag ... On Wed, 23 Nov 2005 06:23:58 -0800, Roy Lewallen wrote: Spice is a great tool. Like every tool one must know how it works, how to use it to its fullest and knowing the tool can hurt you if abused. When introduced to spice for the first time I was told garbage in, garbage out and never assume that computer crunched garbage is anything other than composted garbage. What I've found is that Spice does allow you the luxury of saying "what if" or "how does that affect xxx" even if you are not sure it's real. Allison KB1GMX |
"Standard parts" for rf amps?
OK Jim -
I simulated your question in a first trial. Here is the result: approx. 70MegHz resonance for 100pF, 30mOhm ESR and 5nH for the trace. Surely I would prefer smd chips having better results. BTW: I cannot understand why you're so aggressive and I would prefer that the thread will go in direction of my FIRST posting. I'm doing electronics since I was 12 years old and that is 25 years back. I have for example a patent application made and worked in the communication industry. So you can surely think I know what I'm doing. Thanks! - Henry "RST Engineering (jw)" schrieb im Newsbeitrag ... Agreed, John, 150 MHz is damned near DC for a lot of us, but as yet I have no answer from the "spice" folks for the 1 nf capacitor question. A lot of fancydancing but no answers. Jim |
"Standard parts" for rf amps?
You can that simulate as a rc coupled line of a few steps. That works even
for battery simulations. - Henry "Roy Lewallen" schrieb im Newsbeitrag ... Ken Smith wrote: Heck, that can happen before you hit 1MHz. Check out the ESL and ESR of a 47,000uF capacitor some time. How about dielectric absorption ("soak")? I first encountered this in an electrolytic capacitor being used for generating a sweep of about a minute duration. The capacitor had to be kept shorted for several seconds between sweeps in order for the charge to adequately empty, an equivalent frequency of less than one Hz. Roy Lewallen, W7EL |
"Standard parts" for rf amps?
Thanks Allison!
- Henry schrieb im Newsbeitrag ... On Tue, 22 Nov 2005 12:20:25 +0100, "Henry Kiefer" wrote: Thank Mark! MC and Maxim is not new to me. I thought on list of cheap, easy getting parts with reasonable performance. - Henry Minicircuits the MIMICs and mixers are of most interest and there are inexpensive versions in the line up. What both offer is well characterized RF 50 ohm port parts that behave well in circuits. For example you can build a DBM, can you say for sure what the characteristics will be from say 2-500mhz? Other useful parts from there are VCOs and RF transformers. Allison |
"Standard parts" for rf amps?
"Henry Kiefer" wrote in message ... OK Jim - I simulated your question in a first trial. Here is the result: approx. 70MegHz resonance for 100pF, 30mOhm ESR and 5nH for the trace. Surely I would prefer smd chips having better results. But that wasn't the question. THe question was to simulate a 1000 pf (1 nf) capacitor at 150 MHz. with an inch of lead or an inch of normal pcb trace and tell me what you get. BTW: I cannot understand why you're so aggressive and I would prefer that the thread will go in direction of my FIRST posting. OK by me. I'm doing electronics since I was 12 years old 8 years old. and that is 25 years back. 54 years back. I have for example a patent application made I've got a few more. and worked in the communication industry. 38 years straight now. So you can surely think I know what I'm doing. Then answer the question. Jim |
"Standard parts" for rf amps?
jw\ wrote...
The question was to simulate a 1000 pf (1 nf) capacitor at 150 MHz. with an inch of lead or an inch of normal pcb trace and tell me what you get. Such a question is stupid and incomplete. First of all, in cases where impedance matters, one wouldn't dare use an inch of lead at 150MHz, we'd cut that short, 0.1-inch max. And we certainly wouldn't use an inch of pcb trace unless it was field-controlled with a ground plane. This is true whether a 1nF cap is involved or not. If you were to insist on analyzing an inch of lead, we'd insist on knowing *all* about the ground scene. Since you aggressively put your question without any relevant information about what the ground is like, and where it is, the question is intrinsically-stupid and incomplete. Sorry, jw\, but that's the way it is. BTW: I cannot understand why you're so aggressive ... Indeed. Then answer the question. Answered repeatedly already. -- Thanks, - Win |
"Standard parts" for rf amps?
Mark wrote [WITHOUT CONTEXT]:
there are lots of parts... http://groups.google.com/group/sci.electronics.design/browse_frm/thread/1e72eb22780bfcee/6939ac83d77b8ded?q=don't-click-the-reply-link-that-is-in-plain-sight+To-get-context-the-easy-way+on-Google+zzz+show-options*-*-*-snip-*-*-*-*-the-automated-blockquote-*-*-*+click-THAT-Reply-link |
"Standard parts" for rf amps?
RST Engineering (jw) wrote:
. . . Then answer the question. Did you find my answer to be inadequate or incorrect? If so, in what ways? If not, why do you need it to be answered again? Roy Lewallen, W7EL -- one of the "'spice' folks" |
"Standard parts" for rf amps?
"RST Engineering (jw)" schrieb im Newsbeitrag ... I simulated your question in a first trial. Here is the result: approx. 70MegHz resonance for 100pF, 30mOhm ESR and 5nH for the trace. Surely I would prefer smd chips having better results. But that wasn't the question. THe question was to simulate a 1000 pf (1 nf) capacitor at 150 MHz. with an inch of lead or an inch of normal pcb trace and tell me what you get. Then answer the question. OK - playing on: I got nothing. There is no power supply. No antenna interaction. No thermal noise source. You circuit is bull****! Maybe we have a communication problem and should drink a beer?? - Henry |
"Standard parts" for rf amps?
"Winfield Hill" wrote in message ... jw\ wrote... The question was to simulate a 1000 pf (1 nf) capacitor at 150 MHz. with an inch of lead or an inch of normal pcb trace and tell me what you get. Such a question is stupid and incomplete. No, Win, the question is well formed and quite complete. Sleep off the ten shots of Old Rammycackle and let's have the discussion when you are sober. First of all, in cases where impedance matters, one wouldn't dare use an inch of lead at 150MHz, we'd cut that short, 0.1-inch max. No, Win, neither you nor I would do such a thing. But somebody who is (as the OP posted) new to the RF world would do so without a second thought. You and I have been playing this game all our lives and take self-resonance into account without even thinking about it. However, a student new to the field (as my freshman engineering students are) makes the mistake repeatedly, even when using a decent text called ... um ... The Art Of Something Or Other. When their RF amplifier starts squeeging or motorboating, I tell them that the power supply isn't bypassed well enough, and I'll be damned if the first thing they do is put a BIGGER capacitor on the supply line. I'll then ask them what they think the bypass impedance is and get the stock answer "1/(2*pi*f*c)". Hm, says I, how about the three inches of wire between the capacitor and the supply line. Oh, says them, that's a direct short. Straight wire doesn't have a reactive component. Hm, says I, let's see what the network analyzer says about that. Hm, says student, it says 60 nanohenries. How can that be? Mm, 20 nanohenries per inch for #20 wire sounds about right, so what does that series circuit look like? Hm. Inductive at the frequency of interest. Now, grasshopper, tell me about self-resonance of capacitors with long leads. And we certainly wouldn't use an inch of pcb trace unless it was field-controlled with a ground plane. That's not always an option in commercial gear, Win. This is true whether a 1nF cap is involved or not. If you were to insist on analyzing an inch of lead, we'd insist on knowing *all* about the ground scene. Since you aggressively put your question without any relevant information about what the ground is like, and where it is, the question is intrinsically-stupid and incomplete. If I didn't say what the ground is, then we can assume that I formulated the question without ground plane. 99% of the commercial products run this way. Sorry, jw\, but that's the way it is. Sorry, Win, that's NOT the real world. Jim |
"Standard parts" for rf amps?
On Wed, 23 Nov 2005 15:05:42 -0800, "RST Engineering \(jw\)"
wrote: "Henry Kiefer" wrote in message ... OK Jim - I simulated your question in a first trial. Here is the result: approx. 70MegHz resonance for 100pF, 30mOhm ESR and 5nH for the trace. Surely I would prefer smd chips having better results. But that wasn't the question. THe question was to simulate a 1000 pf (1 nf) capacitor at 150 MHz. with an inch of lead or an inch of normal pcb trace and tell me what you get. The question is unclear. Any component must have a return path, either when you measure it or when you use it in a circuit. The entire loop determines the "lead" inductance. If I solder an axial cap, with 1" of extra leads, onto the end of a hunk of coax, and analyze it with a VNA or TDR, I can bend the cap leads into various fat/flat loops and push the L all over the place. John |
"Standard parts" for rf amps?
And why, Jim, you don't comment my effort?
Maybe I'm newer to rf as you but where is the difference between a microprocessor decoupling from the power supply at 100MegHz and a rf stage at the same frequency? Truly the cpu is more challenging because of the broad used spectrum above 100MegHz. Done PowerPC, PCI stuff and others.... - Henry |
"Standard parts" for rf amps?
RST Engineering (jw) wrote:
"Winfield Hill" wrote in message ... jw\ wrote... The question was to simulate a 1000 pf (1 nf) capacitor at 150 MHz. with an inch of lead or an inch of normal pcb trace and tell me what you get. Such a question is stupid and incomplete. No, Win, the question is well formed and quite complete. Sleep off the ten shots of Old Rammycackle and let's have the discussion when you are sober. It is not a complete question. You could get all sorts of different parasitic inductance values by putting the component near or far from other metallic objects, which usually occurs to some extent in any practical situation. Many other things will affect the answer. You have not yet supplied anything other than a single dimension measurement for the component. If you want the inductance, skin effect, etc. then you would have to give me a dimensioned drawing showing the placement of the wires, the plating material, plating thickness and the internal construction of the capacitor. (You would also have to pay me enough to make it worth me bothering to simulate it.) Your question is incomplete. First of all, in cases where impedance matters, one wouldn't dare use an inch of lead at 150MHz, we'd cut that short, 0.1-inch max. No, Win, neither you nor I would do such a thing. But somebody who is (as the OP posted) new to the RF world would do so without a second thought. You and I have been playing this game all our lives and take self-resonance into account without even thinking about it. However, a student new to the field (as my freshman engineering students are) makes the mistake repeatedly, even when using a decent text called ... um ... The Art Of Something Or Other. When their RF amplifier starts squeeging or motorboating, I tell them that the power supply isn't bypassed well enough, and I'll be damned if the first thing they do is put a BIGGER capacitor on the supply line. I'll then ask them what they think the bypass impedance is and get the stock answer "1/(2*pi*f*c)". Hm, says I, how about the three inches of wire between the capacitor and the supply line. Oh, says them, that's a direct short. Straight wire doesn't have a reactive component. Hm, says I, let's see what the network analyzer says about that. Hm, says student, it says 60 nanohenries. How can that be? Mm, 20 nanohenries per inch for #20 wire sounds about right, so what does that series circuit look like? Hm. Inductive at the frequency of interest. Now, grasshopper, tell me about self-resonance of capacitors with long leads. And we certainly wouldn't use an inch of pcb trace unless it was field-controlled with a ground plane. That's not always an option in commercial gear, Win. Well as you have not specified whether this is "commercial gear" and what type of PCB material, dielectric thickness, trace width etc. of course we can't tell you the answer. Neither could a guy who was going to answer your question by building one and measuring it. He could find one possible answer but there are lots of possible answers which differ because you have not given us a complete problem to solve. This is true whether a 1nF cap is involved or not. If you were to insist on analyzing an inch of lead, we'd insist on knowing *all* about the ground scene. Since you aggressively put your question without any relevant information about what the ground is like, and where it is, the question is intrinsically-stupid and incomplete. If I didn't say what the ground is, then we can assume that I formulated the question without ground plane. 99% of the commercial products run this way. You still gave insufficient information on the wire geometry. I would refute your claim that 99% of commercial products don't use a ground plane. The cell-phone market is in the high hundreds of millions of units this year, and is likely to reach 1 billion units per year next year, and I guarantee you that every one will contain a multi-layer PCB with ground planes and microstrip traces etc. every one of them designed using field simulators and some version of SPICE to model the integrated circuit packages and bondwires, as well as the antenna. I don't believe that this one billion units would fit into the 1% minority of products that you think have ground planes! Sorry, jw\, but that's the way it is. Sorry, Win, that's NOT the real world. Jim Anyhow, until you tell me how long a piece of string is, (to the nearest micron or micro-inch whichever you prefer), I have had enough of this thread. Chris |
"Standard parts" for rf amps?
Am Thu, 24 Nov 2005 09:55:13 -0800 schrieb RST Engineering (jw)
: into account without even thinking about it. However, a student new to the field (as my freshman engineering students are) makes the mistake repeatedly, even when using a decent text called ... um ... The Art Of Something Or Other. When their RF amplifier starts squeeging or motorboating, I tell them that the power supply isn't bypassed well enough, and I'll be damned if the first thing they do is put a BIGGER capacitor on the supply line. Like some of us could lough nicely, when a new guy at a customer (semiconductor fab/asics) of the last company I worked for had to test an RF Chip. Another engineer came to look what the guy is doing, saw he didn't bypass the power supply and recommended to do so. The young engineer put a nice 2200µF electrolytic at the terminals of the lab-power-supply. -- Martin |
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