Mr. D. Self : Why JFET OPamp Servo?

[xrk971]

Funny how so many high negative feedback amps on this forum require a trimpot and constant adjustment, or an opamp servo loop to zero out offset.

 

[AKSA]

All circuits with high NFB will do the same, just like any opamps.
Nothing new.

Uncalled for. We recognise that 'other' designs are not as good as yours, Patrick, but a little modesty is needed, particularly if you are selling product.

The global feedback on the AKSA/Lender is actually very low, only 20dB, I think you missed that.

Hugh

 

[Mark Johnson]

Plenty of zero negative feedback amps require a trimpot for offset adjustment too. Two that come to mind immediately are the First Watt F4 and the First Watt M2. However neither of them need "constant adjustment." You patiently wait for the amp to come all the way up to long term equilibrium temperature, adjust the offset pot once, and then you're done. No more adjustments ever.

 

[xrk971]

Yes, maybe “constant adjusment” was an exaggeration - adjustment is fixed - until the ambient temperature happens to change from winter to summer or AC on vs AC off.