Differential FET-BJT Amplifier PUBLIC

Stripped down version of "Geophone amplifier".

This is a stripped down version of the Geophone amplifier. Since it has no constant-current source, common mode rejection and power supply ripple rejection has been sacrificed for the sake of a simpler circuit.

Note it still has quite low distortion, as nonlinearities of one half are mostly cancelled out by equal and opposite nonlinearities of the other half. This one has a "going into saturation" curve reminiscent of a vacuum tube push-pull amp. Overdrive it and see.

The most critical matched pair are the FET's. If they are mismatched in pinchoff voltage, you will have difficulty balancing the circuit. You may need to change the value of the bias setting resistor R13 to customize the circuit to your FETs.