[sdiy] Dual Matched N JFET from Linear

[Mike Bryant]

The standard Grahem Cohen amplifier gets around those problems - the tightly coupled op-amps on each transistor keep each side of the long-tailed input pair matching.  You can still get a little DC offset, and Midas for example do try to correct for this even those most others don't bother, but all it gives you is another few millivolts of headroom on a 24 volt input signal 🙂

________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of René Schmitz <synth at schmitzbits.de>
Sent: 22 June 2025 11:07
To: synth-diy at synth-diy.org <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Dual Matched N JFET from Linear

On 21.06.2025 22:18, Mike Bryant wrote:
One place you do see FETs quite a lot is the muting output of mixers - they kill thumps well without distorting the output signal.


Sure, signal switching (off in this case). Where circuits tend to be relatively insensitive to the unit variations.

I was thinking more about amplification where the DC offset and matching specs can come into play. Which might require a tightly matched pair.


Cheers,

 René



________________________________

On 2025-06-21 12:53, René Schmitz wrote:
> FETs have large unit to unit variations, good for one-off hobbyist or
> space mission work, but
> annoying to show-stopper for mass production. So you'll not see them
> that often in the wild.




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________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of René Schmitz <synth at schmitzbits.de>
Sent: 22 June 2025 11:07
To: synth-diy at synth-diy.org <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Dual Matched N JFET from Linear

On 21.06.2025 22:18, Mike Bryant wrote:
One place you do see FETs quite a lot is the muting output of mixers - they kill thumps well without distorting the output signal.


Sure, signal switching (off in this case). Where circuits tend to be relatively insensitive to the unit variations.

I was thinking more about amplification where the DC offset and matching specs can come into play. Which might require a tightly matched pair.


Cheers,

 René



________________________________

On 2025-06-21 12:53, René Schmitz wrote:
> FETs have large unit to unit variations, good for one-off hobbyist or
> space mission work, but
> annoying to show-stopper for mass production. So you'll not see them
> that often in the wild.




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