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JFET Common Source DC Amplifier Temperature Compensation


Vladimir Vassilevsky

Jan 1, 1970
D from BC wrote:

What are some ways to temperature compensate a common source JFET DC

+------------Vout (biased for 50% Vdd)
signal--->[ N JFET

Here we go:

Paycheck time :)


DC amp: check
Thermal compensation: check
BW to 2Mhz: check (Looks fast! (1) (2))
Amplifies below rail voltage: check
Inverting output: n/a check
Uses matched dual JFET pack: check
Low noise: op amp noise introduced (eh...might be ok).. check
Parts count: great
Prone to oscillation: dunno yet

(1) No gain!
(2) I suspect thermal compensation can be traded off for more gain by
including negative feedback about the op amp.

Added two resistors. Now there is gain.

In some ways this circuit is like the inclusion of Rs... Gain is
traded off for thermal stability.

This schematics is a sort of the differential amplifier.
Impressive :)

Sure, as I always do.

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant