Integrated low input current JFET amplifier.

摘要

A monolithic IC chip having a differential amplifier comprising a pair of JFETs with their top and back gates electrically isolated to provide a low-leakage-current input to the top gates. The amplifier includes independent bias circuitry for setting the potentials of the JFET back gates to a level close to that of the top gates. This circuitry includes resistive means coupled to the source electrodes of the input JFETs, and operable to establish a low-noise bias point for the back gates. The bias circuitry includes a reference current source comprising a pair of JFETs identical to the input JFETs and arranged to provide a gate-to-source voltage to match that of the input JFETs.