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#1
May 5th 04, 11:39 AM
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Superfast Power MOSFETs for a Linear Amp?
Hi all,
I was thinking about having a go at contriving (I won't say "designing" for obvious reasons) a class 'C' RF amp using MOSFETs instead of the usual BJTs/toobz. They seem - on the face of it at least - ideally suited to the task. I'm just a bit concerned about whether even the fastest ones would be fast enough, even given adequate gate drive. I'd be surprised if they weren't good for at least a few Mhz., but am quite frankly clueless as to MUF. Anyone know? Thanks, p. -- The BBC: licenced at public expense to spread lies. |
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#2
May 5th 04, 12:25 PM
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Paul Burridge wrote:
Hi all, I was thinking about having a go at contriving (I won't say "designing" for obvious reasons) a class 'C' RF amp using MOSFETs instead of the usual BJTs/toobz. They seem - on the face of it at least - ideally suited to the task. I'm just a bit concerned about whether even the fastest ones would be fast enough, even given adequate gate drive. I'd be surprised if they weren't good for at least a few Mhz., but am quite frankly clueless as to MUF. Anyone know? Paul, what is the frequency range and the amplitude ? I assume a 50 Ohm system. Rene -- Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net |
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#3
May 5th 04, 12:32 PM
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"Rene Tschaggelar" wrote in message ...
Paul Burridge wrote: Hi all, I was thinking about having a go at contriving (I won't say "designing" for obvious reasons) a class 'C' RF amp using MOSFETs instead of the usual BJTs/toobz. They seem - on the face of it at least - ideally suited to the task. I'm just a bit concerned about whether even the fastest ones would be fast enough, even given adequate gate drive. I'd be surprised if they weren't good for at least a few Mhz., but am quite frankly clueless as to MUF. Anyone know? Paul, what is the frequency range and the amplitude ? I assume a 50 Ohm system. Yep, that's a good question for Win. Suitable general purpose MOSFETs for RF finals (probably only feasible in the shortwave range) and best way to drive them. Let's say the more power the better (10-200W). SioL |
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#4
May 5th 04, 03:54 PM
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On Wed, 05 May 2004 13:25:52 +0200, Rene Tschaggelar
wrote: Paul Burridge wrote: Hi all, I was thinking about having a go at contriving (I won't say "designing" for obvious reasons) a class 'C' RF amp using MOSFETs instead of the usual BJTs/toobz. They seem - on the face of it at least - ideally suited to the task. I'm just a bit concerned about whether even the fastest ones would be fast enough, even given adequate gate drive. I'd be surprised if they weren't good for at least a few Mhz., but am quite frankly clueless as to MUF. Anyone know? Paul, what is the frequency range and the amplitude ? I assume a 50 Ohm system. Yeah, 50 in; 50-75 out say. As for frequency, that's what I'm trying to establish: the highest useable frequency device for say 50W-100W out. Amplitude's subservient to power. What kind of frequency upper limit might be achievable? Say with the best gate driver arrangement conceivable? -- The BBC: licenced at public expense to spread lies. |
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#5
May 6th 04, 01:13 AM
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Paul Burridge wrote:
On Wed, 05 May 2004 13:25:52 +0200, Rene Tschaggelar wrote: Paul Burridge wrote: Hi all, I was thinking about having a go at contriving (I won't say "designing" for obvious reasons) a class 'C' RF amp using MOSFETs instead of the usual BJTs/toobz. They seem - on the face of it at least - ideally suited to the task. I'm just a bit concerned about whether even the fastest ones would be fast enough, even given adequate gate drive. I'd be surprised if they weren't good for at least a few Mhz., but am quite frankly clueless as to MUF. Anyone know? Paul, what is the frequency range and the amplitude ? I assume a 50 Ohm system. Yeah, 50 in; 50-75 out say. As for frequency, that's what I'm trying to establish: the highest useable frequency device for say 50W-100W out. Amplitude's subservient to power. What kind of frequency upper limit might be achievable? Say with the best gate driver arrangement conceivable? Mosfets in the MRF5xx series (511, 521 for example) have been used up to the 10 meter band with good results. A pair of them can give at least 50w pep output. Depending on the input/output circuitry used and the transistor they require 12-28v power supply. Layout is somewhat critical. |
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#6
May 6th 04, 05:27 PM
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On Wed, 05 May 2004 20:13:01 -0400, Ken Scharf
wrote: Mosfets in the MRF5xx series (511, 521 for example) have been used up to the 10 meter band with good results. A pair of them can give at least 50w pep output. Depending on the input/output circuitry used and the transistor they require 12-28v power supply. Layout is somewhat critical. THanks, very interesting. I wonder if anyone's tried paralleling up half a dozen of 'em for more power? -- The BBC: licenced at public expense to spread lies. |
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#7
May 6th 04, 05:56 PM
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THanks, very interesting. I wonder if anyone's tried paralleling up
half a dozen of 'em for more power? ================================== Mind in-&output capacitances ,which add-on when parallelling. Frank GM0CSZ / KN6WH |
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#8
May 6th 04, 05:56 PM
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THanks, very interesting. I wonder if anyone's tried paralleling up
half a dozen of 'em for more power? ================================== Mind in-&output capacitances ,which add-on when parallelling. Frank GM0CSZ / KN6WH |
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#9
May 6th 04, 05:27 PM
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On Wed, 05 May 2004 20:13:01 -0400, Ken Scharf
wrote: Mosfets in the MRF5xx series (511, 521 for example) have been used up to the 10 meter band with good results. A pair of them can give at least 50w pep output. Depending on the input/output circuitry used and the transistor they require 12-28v power supply. Layout is somewhat critical. THanks, very interesting. I wonder if anyone's tried paralleling up half a dozen of 'em for more power? -- The BBC: licenced at public expense to spread lies. |
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#10
May 6th 04, 01:13 AM
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Paul Burridge wrote:
On Wed, 05 May 2004 13:25:52 +0200, Rene Tschaggelar wrote: Paul Burridge wrote: Hi all, I was thinking about having a go at contriving (I won't say "designing" for obvious reasons) a class 'C' RF amp using MOSFETs instead of the usual BJTs/toobz. They seem - on the face of it at least - ideally suited to the task. I'm just a bit concerned about whether even the fastest ones would be fast enough, even given adequate gate drive. I'd be surprised if they weren't good for at least a few Mhz., but am quite frankly clueless as to MUF. Anyone know? Paul, what is the frequency range and the amplitude ? I assume a 50 Ohm system. Yeah, 50 in; 50-75 out say. As for frequency, that's what I'm trying to establish: the highest useable frequency device for say 50W-100W out. Amplitude's subservient to power. What kind of frequency upper limit might be achievable? Say with the best gate driver arrangement conceivable? Mosfets in the MRF5xx series (511, 521 for example) have been used up to the 10 meter band with good results. A pair of them can give at least 50w pep output. Depending on the input/output circuitry used and the transistor they require 12-28v power supply. Layout is somewhat critical. |
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