Not quite yet 
........ but I suggest this offset adjustment solution as being less evasive ( a 5k - 1K pot should work) leave out the trim pot on the first differential, otherwise it's complete in my humble opinion, but it is Jeff's call.
solution........
Jam
........ but I suggest this offset adjustment solution as being less evasive ( a 5k - 1K pot should work) leave out the trim pot on the first differential, otherwise it's complete in my humble opinion, but it is Jeff's call. solution........
Jam
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Hi Jam:
OK, I look forward to your call ....
mlloyd1
OK, I look forward to your call ....
mlloyd1
Hi Michael,
Welcome to the best thread on the forum........
Probably the mirror improvements, but the design is converging into a fine amplifier but is excellent as it stands.
I need to talk to you after the first of the year about that pre-amp topology we discussed some time back. I may have some boards for you.
Jam
Regarding beefcake, I have been seriously intending on replacing TL431 with just an appropriate value Zener/led combination as a voltage reference and using a trim pot, to dial up the bias voltage, then you can use small value polypropylene caps instead of large electrolytics as used with TL431.
For the purpose of biasing up a lateral fet source follower output stage
Maybe 3 or 4 green leds or appropriate Zener with trimpot.
Or just keep throwing leds at the bias circuit till near enough is good enough (ie anything that achieves around 1.5A to 2A) and just have dc offset.
For the purpose of biasing up a lateral fet source follower output stage
Maybe 3 or 4 green leds or appropriate Zener with trimpot.
Or just keep throwing leds at the bias circuit till near enough is good enough (ie anything that achieves around 1.5A to 2A) and just have dc offset.
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Hi Mark,
Oops! As drawn neither makes any sense. The compensation resistor needs to be outside the bias spreader, not inside it. (Then it will be clear that the capacitor just goes across the spreader.)
Thanks for catching that!
Cheers,
Jeff.
Been scratching my head about that one.
My current TL431 bias setup for ref.
Idea A, GLED431 replaces TL431, or B? (neither have been built). My rambling thoughts lead on to should I use the LTP regulator? OK It's getting complicated again, do you really need all this? then thought, what's wrong with the amplified diode if a thermistor is included? Can't be that good if people are moving away, need a low noise Vref......... Go to Line 3
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Just reading green leds have a negative temperature coefficient of between -3.6mV/K to -5.2mV/K. That could actually be quite useful for hockey pucks too.
I like dumb stuff that just works.
https://www.onsemi.com/pub/Collateral/TND328-D.PDF
I like dumb stuff that just works.
https://www.onsemi.com/pub/Collateral/TND328-D.PDF
I think that might be a little difficult, the jump between 4 & 5 LED's would be not enough bias current and Oh bugger, I need bigger heatsinks!
Add a 4.1V Zener (or any other) to the mix of green leds to get what you need.I think that might be a little difficult, the jump between 4 & 5 LED's would be not enough bias current and Oh bugger, I need bigger heatsinks!