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Thought this was puzzling...
I came across this site... and picture. Are these diodes an attempt at
thermal tracking for the bias? http://www.worldwidedx.com/gallery/a...pad_and_diodes www.telstar-electronics.com |
Thought this was puzzling...
"Telstar Electronics" wrote in message oups.com... I came across this site... and picture. Are these diodes an attempt at thermal tracking for the bias? http://www.worldwidedx.com/gallery/a...pad_and_diodes www.telstar-electronics.com No, someone has just put them in as an attempt to protect against reverse polarity! Slightly mad. |
Thought this was puzzling...
Paul wrote:
No, someone has just put them in as an attempt to protect against reverse polarity! Slightly mad. Is that what you think that is???? Why have the diodes right on top of the transistors? No, I think that was an effort to temp track the bias. Well, at least they were trying. Unfortunately, don't think that's going to work that way... LOL www.telstar-electronics.com |
Thought this was puzzling...
On 24 Sep 2006 08:53:06 -0700, "Telstar Electronics"
wrote: I came across this site... and picture. Are these diodes an attempt at thermal tracking for the bias? http://www.worldwidedx.com/gallery/a...pad_and_diodes www.telstar-electronics.com It provides negative thermal feedback. The voltage across the transistor will decrease as the transistor temperature increases. This prevents thermal runaway. |
Thought this was puzzling...
wrote:
It provides negative thermal feedback. The voltage across the transistor will decrease as the transistor temperature increases. This prevents thermal runaway. That's what it's supposed to do... I claim it can't work as shown. It's not quite that simple as tacking a few diodes on the bias circuit and laying them on top of the transistors... LOL www.telstar-electronics.com |
Thought this was puzzling...
Tacking the diodes on to the case of the transistor works better than
attaching them to the heat sink due to the relatively slow thermal response, the heat sink changes temperature slower that the cap on the transistor. If you want as fast a response as possible then the diodes are placed about as well as you can get. I've also seen small diodes clipped on to the flange of TO-3 style cases for the same reason. I've seen some high power transistors used for motor drive and high frequency inverter use that has the temperature sensing diode, or thermistor, built inside of the package. http://pdf1.alldatasheet.co.kr/datas...50HM75STG.html As the temperature of the base-emitter junction goes up the required forward voltage for a given base current decreases. If nothing was done, the base-emitter bias voltage held fixed, the base current for increases and thus the collector current too. Of course increased collector current results in more power dissipation, thus more heat and higher resulting temperature, i.e. thermal runaway. The diode used for bias temperature compensation has to very closely match the Ib-Vbe curve of the transistor to work effectively . You can't use just any diode and expect it to work very well. The problem with mounting the diode on the heat sink is the large thermal mass. If the transistor starts to go in to thermal runaway the heat sink will take a significant time to heat up, thus reducing the bias to the base-emitter junction, long after the runaway has started. You want to get the compensation right as soon as possible, reduce the base-emitter bias, before the junction gets too hot. The small cap on the transistor will heat up much faster that anything else giving the designer a chance to design a fast responding bias circuit which could avoid transistor destruction. Diode bias circuits are on their way out in favor of more advance bias circuits. The chief problem with diode bias compensation is either too much, the transistor gets starved for needed bias current, or not enough, tendency to go in to thermal runaway. The reason the transistor can get starved for bias current is simple. The Beta, current gain, of a bipolar transistor is not constant over the operating range, it varies based on the instantaneous operating point. At some point the gain is so low that the current flowing through the bias compensation diode may drop to a low value, or go to zero, limiting the bias current forcing the operation to go non-linear over part of the cycle. That's why some of the simple diode bias circuits draw so much standing current. It has to supply the worst case bias current. Newer active bias circuits use a voltage source type design. The bias voltage tracks the transistor temperature and since it is a "voltage source" there is no practical limitation on the bias current. The transistor will draw what it needs without being limited by the current limiting resistors in the diode bias type of circuit. I'm sure somebody is going to nit-pick this post. They're welcomed. -- Regards, Leland C. Scott KC8LDO "Telstar Electronics" wrote in message ups.com... wrote: It provides negative thermal feedback. The voltage across the transistor will decrease as the transistor temperature increases. This prevents thermal runaway. That's what it's supposed to do... I claim it can't work as shown. It's not quite that simple as tacking a few diodes on the bias circuit and laying them on top of the transistors... LOL www.telstar-electronics.com |
Thought this was puzzling...
On Sun, 24 Sep 2006 23:30:24 -0400, "LeIand C. Scot"
wrote in : snip I'm sure somebody is going to nit-pick this post. They're welcomed. Not picking nits, just taking a different approach..... Thermal bias compensation works to a point but neglects one important issue: it takes time for heat to travel from the junction to the outside of the package, and thermal runaway can happen faster than a -thermal- compensation circuit can respond to it. Since the heat buildup is due to excessive EC current, it makes more sense to control the EC current directly. There are two solutions that use this approach. One is to include a resistor on the emitter with a TC opposite of the transistor. Not precision but much faster response. The other is to monitor the EC voltage and the base current; send both measurements to a differential OP amp and use the output as feedback for the bias regulator. I tend to favor the first choice because it has the added benefit of improving linearity. I would only use the second choice in a high profit, 'stick-it-to-the-consumer' product. |
Thought this was puzzling...
On 24 Sep 2006 17:17:29 -0700, "Telstar Electronics"
wrote: wrote: It provides negative thermal feedback. The voltage across the transistor will decrease as the transistor temperature increases. This prevents thermal runaway. That's what it's supposed to do... I claim it can't work as shown. It's not quite that simple as tacking a few diodes on the bias circuit and laying them on top of the transistors... LOL Why does every post griffey does end with LOL???? ************************************************** ** There are a good many who will be surprised by this seasons NY Knicks. I think larry made a mistake and how many would be surprised if the Knicks make the playoffs and go to the second round? ************************************************** ** |
Thought this was puzzling...
On a sunny day (Sun, 24 Sep 2006 23:30:24 -0400) it happened "LeIand C. Scot"
wrote in : I'm sure somebody is going to nit-pick this post. They're welcomed. No it is a nice post, I appreciate it, we should have more like this. |
Thought this was puzzling...
Bill Gates wrote:
Why does every post griffey does end with LOL????' Because I can't help but laugh at some of the stupid comments I read out here. Bottom line... that circuit with those two little doides isn't doing any temperature tracking for the bases of those transistors. Several things are wrong: 1.) The bias that feeds those bases needs to be very low impedance... on the order of around 5 Ohms. There is no freaking way that those little diodes could carry enough bleeder current to feed those bases. 2.) And if that's not enough... there is another fatal flaw with that scheme. It's effectively paralleling diodes... the small diodes hanging on top... and the diodes in the base-emitter junction of the power transistors. Electronics 101 says that it's a bad plan to parallel diodes (why you never just parallel bipolar transistors!). The reason... because one will always hog the current... and starve the other. One will be on... the other is cut off. You will never get them both on at one time. Soooooo... when this happens... you can't get any tracking... because only one diode is on at a time. 3.) Having the sensing on top of the transistors is a poor location. The internal die is in intimate contact with the heat sink... not the top! The het sink... preferably near the device is the proper location for any tracking device. Like I said before... it's not quite that simple just tacking a couple diodes on top of the devices... LOL www.telstar-electronics.com |
Thought this was puzzling...
On a sunny day (25 Sep 2006 04:40:57 -0700) it happened "Telstar Electronics"
wrote in .com: Bill Gates wrote: Why does every post griffey does end with LOL????' Because I can't help but laugh at some of the stupid comments I read out here. Bottom line... that circuit with those two little doides isn't doing any temperature tracking for the bases of those transistors. Several things are wrong: 1.) The bias that feeds those bases needs to be very low impedance... on the order of around 5 Ohms. There is no freaking way that those little diodes could carry enough bleeder current to feed those bases. That lookes like 1A diodes, and would be no problem. All you phantasies, your lack of a decent Pi filter, you failing to grasp heat rises upwards (you can hold your hand next to a candle but not above it), so diodes _above_ transistors is _good_, but I will show you how the profies do it, this is what runs he http://www.cbtricks.com/radios/rci/r...0_main_sch.gif It is a big gif, go to bottom left corner, there is the amp, the Pi filter, and the temp stabilaziation a bit to the right of that. Oh, and the on board SWR meter (all teh way at the left). And here is the amp PCB layout: http://www.cbtricks.com/radios/rci/r...rf-amp_pcb.htm It is only 150W PEP, but it works great here. And no harmonics with that filter. Oops, do I see 2 diodes in parallel? Must be me eyes ;-) Oops it is 1N4001. So now copy-cat the Pi filter? Oh what, you have the whole diagram. I have to point out that the Ranger 2970 is a nice set, clocked many hundreds of hours here, not one problem. Good sound quality too. OK over to Telstar for the Telstar diagram, hey if Ranger publishes theirs, what have you got to hide? And they are making $$$$ |
Thought this was puzzling...
Jan Panteltje wrote:
OK over to Telstar for the Telstar diagram, hey if Ranger publishes theirs, what have you got to hide? And they are making $$$$ That's Ranger's business... not to be confused with mine. http://auctions.yahoo.com/i:SkyWave%...fier:117239910 |
Thought this was puzzling...
"Bill Gates" wrote...
Why does every post griffey does end with LOL???? I do hope it's not catching... LOL. Peter. |
Thought this was puzzling...
On Sun, 24 Sep 2006 21:59:32 -0700, Frank Gilliland wrote:
On Sun, 24 Sep 2006 23:30:24 -0400, "LeIand C. Scot" wrote in : snip I'm sure somebody is going to nit-pick this post. They're welcomed. Not picking nits, just taking a different approach..... Thermal bias compensation works to a point but neglects one important issue: it takes time for heat to travel from the junction to the outside of the package, and thermal runaway can happen faster than a -thermal- compensation circuit can respond to it. Exactly. That's why those diodes are place on the ceramic cap of the device and not on the heat sink. Since the heat buildup is due to excessive EC current, it makes more sense to control the EC current directly. There are two solutions that use this approach. One is to include a resistor on the emitter with a TC opposite of the transistor. Not precision but much faster response. This is done in many audio amps. The chief problem is the negative feedback introduced by the emitter resistor. At auto frequencies this resistor is bypassed by a rather large electrolytic capacitor sized such that at the lowest frequency of interest the reactance is much smaller that the emitter resistor value. Thus the "AC" gain isn't affected much by the emitter resistor. Believe it or not I've seen many of the old Motorola RF devices use internal emitter resistors. Those took the form of many small tungsten bonding wires from different areas of the emitter structure to the emitter terminal. The main idea there was the many wires, resistors, in parallel resulted in a very small overall emitter resistor. Also they found that a problem called "second break down" would occur if they didn't do this. What it amounted too was local hot spots, thermal runaway, in tiny areas of the transistor's emitter structure. I think the term they used for RF devices built this way was "emitter ballasting". The other is to monitor the EC voltage and the base current; send both measurements to a differential OP amp and use the output as feedback for the bias regulator. You would have to look at the "DC" emitter current minus the "AC" component, which I don't think is going to be so easy to do. Regards, Leland C. Scott KC8LDO |
Thought this was puzzling...
Leland C. Scott wrote:
Exactly. That's why those diodes are place on the ceramic cap of the device and not on the heat sink. Having the sensing on top of the transistors is a poor location. The internal die is in intimate contact with the heat sink... not the top! The heat sink... preferably near the device is the proper location for any tracking device. http://auctions.yahoo.com/i:SkyWave%...fier:117239910 |
Thought this was puzzling...
"Telstar Electronics" wrote in message ups.com... Leland C. Scott wrote: Exactly. That's why those diodes are place on the ceramic cap of the device and not on the heat sink. Having the sensing on top of the transistors is a poor location. The internal die is in intimate contact with the heat sink... not the top! The heat sink... preferably near the device is the proper location for any tracking device. Are you really that dense? |
Thought this was puzzling...
On Mon, 25 Sep 2006 19:06:49 -0400, "Leland C. Scott"
wrote: +++Believe it or not I've seen many of the old Motorola RF devices use +++internal emitter resistors. Those took the form of many small tungsten +++bonding wires from different areas of the emitter structure to the emitter +++terminal. The main idea there was the many wires, resistors, in parallel +++resulted in a very small overall emitter resistor. Also they found that a +++problem called "second break down" would occur if they didn't do this. +++What it amounted too was local hot spots, thermal runaway, in tiny areas +++of the transistor's emitter structure. I think the term they used for RF +++devices built this way was "emitter ballasting". ********* I have never seen tungstun bonding wire. All I have ever seen is gold. You need a soft malible metal to bond to the die pads on any semicondcutor. The bond wire is sonic heated to the aluminum metal die pad. This forms the nice ball on the die pad that is a weld of the aluminum and gold. Tungstun is far to hard a metal for bonding. Emmitter ballasting is done on the die within the emmitter matrix. There are several metods of fabricating an RF transistor. Major factors are power, frequency and device operating point. For most transistors operating below 50 MHz use an interdigitated emmitter geometry. Incorparated within are current balancing resistors in the emmitter matrix. This does increase die size and reduces gain. It does spread heat and current more evenly through the die. Interdigitated emmitters will have multiple bond wires. |
Thought this was puzzling...
Peter wrote:
I do hope it's not catching... LOL. It is... if you stick around and read some of the techno-babble on this group... LOL www.telstar-electronics.com |
Thought this was puzzling...
U-Know-Who wrote:
Are you really that dense? Thanks for that great post... you really add a lot to any conversation. www.telstar-electronics.com |
Thought this was puzzling...
LeIand C. Scot wrote:
Tacking the diodes on to the case of the transistor works better than attaching them to the heat sink due to the relatively slow thermal response, the heat sink changes temperature slower than the cap on the transistor. That's simply not true... while the heat sinks response might be a bit slower... it's a much better indicator of the temp of the transistor die. The ceramic cap on those transistors will overshoot the die temp in both directions because of it's poor thermal contact with the die. www.telstar-electronics.com |
Thought this was puzzling...
On a sunny day (26 Sep 2006 05:33:33 -0700) it happened "Telstar Electronics"
wrote in .com: LeIand C. Scot wrote: Tacking the diodes on to the case of the transistor works better than attaching them to the heat sink due to the relatively slow thermal response, the heat sink changes temperature slower than the cap on the transistor. That's simply not true... while the heat sinks response might be a bit slower... it's a much better indicator of the temp of the transistor die. The ceramic cap on those transistors will overshoot the die temp in both directions This is not correct. there is no 'overshoot' in temp possible. Unless you know how to heat solder to 250C with a 200C soldering iron? An other Telstar miracle ;-)? The thermal response will be faster, resulting in better protection. A slower response could result in reducing current too late. |
Thought this was puzzling...
Jan Panteltje wrote:
This is not correct. there is no 'overshoot' in temp possible. Unless you know how to heat solder to 250C with a 200C soldering iron? An other Telstar miracle ;-)? The thermal response will be faster, resulting in better protection. A slower response could result in reducing current too late. You're right... overshoot was the wrong word. I think you knew what I meant... but if you didn't... I'll clarify. There is no friggin' way... having a sensing device on the ceramic cap of those transistors tracks the die temp as good as having that same tracking device in close proximity on the geat sink. www.telstar-electronics.com |
Thought this was puzzling...
"james" wrote in message ... On Mon, 25 Sep 2006 19:06:49 -0400, "Leland C. Scott" wrote: +++Believe it or not I've seen many of the old Motorola RF devices use +++internal emitter resistors. Those took the form of many small tungsten +++bonding wires from different areas of the emitter structure to the emitter +++terminal. The main idea there was the many wires, resistors, in parallel +++resulted in a very small overall emitter resistor. Also they found that a +++problem called "second break down" would occur if they didn't do this. +++What it amounted too was local hot spots, thermal runaway, in tiny areas +++of the transistor's emitter structure. I think the term they used for RF +++devices built this way was "emitter ballasting". ********* I have never seen tungstun bonding wire. All I have ever seen is gold. Correct. That's a mistake on my part. You need a soft malible metal to bond to the die pads on any semicondcutor. The bond wire is sonic heated to the aluminum metal die pad. This forms the nice ball on the die pad that is a weld of the aluminum and gold. Tungstun is far to hard a metal for bonding. I did read in the Motorola manual they did, or tried, to use it in a stack up of metals since they saw a problem with electromigration of the gold used in the bonding wires with the silicon base material. Emmitter ballasting is done on the die within the emmitter matrix. Correct. The two methods I did read about are polysicicon resistors or Nichrome resistors made on the chip. There are several metods of fabricating an RF transistor. Major factors are power, frequency and device operating point. For most transistors operating below 50 MHz use an interdigitated emmitter geometry. Incorparated within are current balancing resistors in the emmitter matrix. This does increase die size and reduces gain. It does spread heat and current more evenly through the die. Interdigitated emmitters will have multiple bond wires. For those really interested in the details I found the PDF document below that goes in to it a bit more. rfwireless.rell.com/pdfs/AN_IRFPT.pdf -- Regards, Leland C. Scott KC8LDO |
Thought this was puzzling...
"Telstar Electronics" wrote in message oups.com... Like I said before... it's not quite that simple just tacking a couple diodes on top of the devices... LOL http://perso.orange.fr/f6itv/p2032001.htm (look at location of diodes in photo at right side) -- Regards, Leland C. Scott KC8LDO |
Thought this was puzzling...
LeIand C. Scot wrote:
http://perso.orange.fr/f6itv/p2032001.htm (look at location of diodes in photo at right side) Yes, this method is similar to a few "reference" designs shown in the Motorola RF Data Manual . This is a poor method for two resaons. The first is what I explained before... trying to get two diodes in parallel to turn on together is very difficult... if not impossible on a repeatable basis. Second, the emitters you are feeding with the DC bias are very low impedance. This creates its own problem when attempting to control the base current. This biasing scheme with temp compensation is a "brute force" method that dissipates large amounts of power... and plain doesn't work well. It's not the first time that circuits shown in a reference manual are not production ready. Motorola also shows a much better method of temp comp bias in that same data manual. It uses an op amp and sink mounted thermistor. I'm also using an "active" approach to the temp comp bias in my amplifier... but a totally different circuit using a bipolar transistor as the sense and gain mechanism. I can hold the 500mA bias to 10% from -30 to +85C. www.telstar-electronics.com |
Thought this was puzzling...
On 25 Sep 2006 16:27:30 -0700, "Telstar Electronics"
wrote in . com: Leland C. Scott wrote: Exactly. That's why those diodes are place on the ceramic cap of the device and not on the heat sink. Having the sensing on top of the transistors is a poor location. It's better than the heat sink. The internal die is in intimate contact with the heat sink... not the top! Wrong. The ceramic package isn't hollow; on the contrary, it contacts more of the junction's surface area than the heat sink flange (which, BTW, doesn't make "intimate contact" with any part of the junction because it is insulated from the die by the Be Oxide substrate). The fact is that a transient pulse can heat and blow the junction before it can dissipate into the -anything-, which it's more likely to happen when the transistor is already hot from normal operation. The heat sink... preferably near the device is the proper location for any tracking device. What part of "heat sink" don't you understand? |
Thought this was puzzling...
Frank Gilliland wrote:
Wrong. The ceramic package isn't hollow; on the contrary, it contacts more of the junction's surface area than the heat sink flange (which, BTW, doesn't make "intimate contact" with any part of the junction because it is insulated from the die by the Be Oxide substrate). If the ceramic cap is tied so well to the heat source internal to the transistor... then why don't you just attach the heat sink to the ceramic caps on your new design?... LOL www.telstar-electronics.com |
Thought this was puzzling...
On 26 Sep 2006 17:15:35 -0700, "Telstar Electronics"
wrote in . com: Frank Gilliland wrote: Wrong. The ceramic package isn't hollow; on the contrary, it contacts more of the junction's surface area than the heat sink flange (which, BTW, doesn't make "intimate contact" with any part of the junction because it is insulated from the die by the Be Oxide substrate). If the ceramic cap is tied so well to the heat source internal to the transistor... then why don't you just attach the heat sink to the ceramic caps on your new design?... LOL Actually, that's not such a bad idea. Computer processors and other chips are encased in ceramic and the heat sinks are typically mounted on top. Having an additional heat sink on the top of the transistor certainly can't hurt. I'll check into this and see if it's do-able. Thanks, Brian! |
Thought this was puzzling...
Frank Gilliland wrote:
Actually, that's not such a bad idea. Computer processors and other chips are encased in ceramic and the heat sinks are typically mounted on top. Having an additional heat sink on the top of the transistor certainly can't hurt. I'll check into this and see if it's do-able. I hate to tell you that processor chips (and some others) are specially designed to attach the sink on the top... the RF transistors we're talking about are not. www.telstar-electronics.com |
Thought this was puzzling...
On 26 Sep 2006 17:29:43 -0700, "Telstar Electronics"
wrote in .com: Frank Gilliland wrote: Actually, that's not such a bad idea. Computer processors and other chips are encased in ceramic and the heat sinks are typically mounted on top. Having an additional heat sink on the top of the transistor certainly can't hurt. I'll check into this and see if it's do-able. I hate to tell you that processor chips (and some others) are specially designed to attach the sink on the top... the RF transistors we're talking about are not. And Viagra was designed to be a heart medication. What's your point? |
Thought this was puzzling...
Frank Gilliland wrote:
And Viagra was designed to be a heart medication. I thought it was for male pattern baldness initially. |
Thought this was puzzling...
"Telstar Electronics" wrote in message ups.com... Frank Gilliland wrote: Wrong. The ceramic package isn't hollow; on the contrary, it contacts more of the junction's surface area than the heat sink flange (which, BTW, doesn't make "intimate contact" with any part of the junction because it is insulated from the die by the Be Oxide substrate). If the ceramic cap is tied so well to the heat source internal to the transistor... then why don't you just attach the heat sink to the ceramic caps on your new design?... LOL www.telstar-electronics.com You're a ****ing idiot dickhead. You simply don't have any common sense. |
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"U-Know-Who" wrote:
www.telSLAP-electronics.com You're a ****ing idiot dickhead. You simply don't have any common sense. He gets to post his free google spam sig with every reply tho.. |
Thought this was puzzling...
"Telstar Electronics" wrote in message oups.com... Frank Gilliland wrote: Actually, that's not such a bad idea. Computer processors and other chips are encased in ceramic and the heat sinks are typically mounted on top. Having an additional heat sink on the top of the transistor certainly can't hurt. I'll check into this and see if it's do-able. I hate to tell you that processor chips (and some others) are specially designed to attach the sink on the top... the RF transistors we're talking about are not. You really are more of moron than thought. |
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"Steveo" wrote in message ... Frank Gilliland wrote: And Viagra was designed to be a heart medication. I thought it was for male pattern baldness initially. They all fix other two. Even if transplants are in order, the new esteem will find the bills for the other two. |
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"Steveo" wrote in message ... "U-Know-Who" wrote: www.telSLAP-electronics.com You're a ****ing idiot dickhead. You simply don't have any common sense. He gets to post his free google spam sig with every reply tho.. But I still love snipping it in my reply. Of course, he'll make another wise and omnipotent statement he |
Thought this was puzzling...
"U-Know-Who" wrote:
"Steveo" wrote in message ... Frank Gilliland wrote: And Viagra was designed to be a heart medication. I thought it was for male pattern baldness initially. They all fix other two. Even if transplants are in order, the new esteem will find the bills for the other two. Or once you start banging again in your old age, we can sell you some heart medicine too. Billionaires. |
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On 26 Sep 2006 16:10:26 -0700, "Telstar Electronics"
wrote in .com: LeIand C. Scot wrote: http://perso.orange.fr/f6itv/p2032001.htm (look at location of diodes in photo at right side) Yes, this method is similar to a few "reference" designs shown in the Motorola RF Data Manual . This is a poor method for two resaons. The first is what I explained before... trying to get two diodes in parallel to turn on together is very difficult... if not impossible on a repeatable basis. In the link above the diodes are not in parallel at all. Look at the schematic. In the link you initially provided they are indeed in parallel, but that doesn't mean they are intended to conduct equal currents. If that were the case then they would have current equalizing resistors in series with each diode. From what I can see in the picture, it's clear that only one diode will be working at any given time: the hot one. And I'm sure that's exactly what was intended. Second, the emitters you are feeding with the DC bias are very low impedance. Very low voltage, too. Some might even call it a "ground potential". The bases, on the other hand...... This creates its own problem when attempting to control the base current. This biasing scheme with temp compensation is a "brute force" method that dissipates large amounts of power... and plain doesn't work well. Apparently it works well enough for a homebrew amp. It's not the first time that circuits shown in a reference manual are not production ready. Hey, look what I found on a quick google search: ================ On 31 Jul 2005 15:58:33 -0700, "Professor" wrote in .com: Frank... I wish I was like you... never wrong... and never had to be corrected. Yes, I already knew that, Brian. I tried to turn you onto the right path years ago when you were hacking basic Motorola AN circuits that were intended to be starting designs for engineers, not finished products to be built by CB ampheads. But you were just too impatient to get your "product" sold and get your share of that illegal market. After damage control backfired in your face (because of your lack of education) you vanished. Now you pop back up to spam the group every time you think you have an improvement. You haven't made very many changes, but look at the ones you -did- make -- all were suggestions that I made when I told you all the reasons your amp sucked. Maybe you learned those things from me or maybe somewhere else, but I was right and you know it...... ================ So contrary to recent opinion polls, it's clear that you -can- learn things. You just can't admit that you learned anything from someone else because that might be bad for business. Motorola also shows a much better method of temp comp bias in that same data manual. It uses an op amp and sink mounted thermistor. I'm also using an "active" approach to the temp comp bias in my amplifier... but a totally different circuit using a bipolar transistor as the sense and gain mechanism. I can hold the 500mA bias to 10% from -30 to +85C. Hey Jan, wanna know why Brian won't cut loose his schematic? Because Brian is a hack and his special bias circuit was most likely ripped from this link, which was posted in this group a couple years ago: http://www.ifwtech.co.uk/g3sek/tr-bias/tr-bias1.htm |
Thought this was puzzling...
Frank Gilliland wrote:
Hey Jan, wanna know why Brian won't cut loose his schematic? Because Brian is a hack and his special bias circuit was most likely ripped from this link, which was posted in this group a couple years ago: http://www.ifwtech.co.uk/g3sek/tr-bias/tr-bias1.htm Yes Frank... look for an ally. Lord knows you need one... LOL www.telstar-electronics.com |
Thought this was puzzling...
Frank Gilliland wrote:
http://www.ifwtech.co.uk/g3sek/tr-bias/tr-bias1.htm Thanks Frank for posting this link. It supports what I've been saying all along about the plain-old diode method working like crap. So why don't you go ahead and use that method on your new amp... LOL www.telstar-electronics.com |
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