Stabilized direct coupled amplifier having improved frequency response and minimum intermodulation distortion

Claim 1

A stabilized direct coupled operational amplifier comprising: a summing junction for receiving a signal to be amplified; at least one stage of amplification for said signal having first and second inputs and an output; an insulated gate field effect transistor having a gate element, a source element, and a drain element; means connecting said gate element to said summing junction; means connecting said source element to said amplifier first input; a source of bias voltage; means connecting said drain element to said voltage source; a stabilizer amplifier having an input and an output, means connecting said summing junction to said stabilizer amplifier input for supplying any signal at said junction to said stabilizer amplifier; a demodulator means connected to said stabilizer amplifier output and to said amplifier second input for demodulating the output of said stabilizing amplifier and applying said demodulated output to said stage; an oscillator for producing a constant fRequency output signal; means connecting said oscillator output to said demodulator for operating said demodulator at said frequency; modulator means connected to said stabilizer input and to said oscillator output for modulating said stabilizer input at said frequency; overload detection means having an input connected to the output of said stage of amplification for producing an output signal upon the occurrence of an overload; and means connected to said overload detection means for applying said output signal to said oscillator and said modulator thereby and for disabling said oscillator and modulator to prevent current flow to said amplifier stage and said stabilizer amplifier.