Importance

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Abstract

An amplifier circuit employs a differential amplifier having first and second differential inputs and having an output for providing an output signal which varies according to a difference between magnitudes of input signals provided at the first and second inputs, a high impedance front end which is coupled to the first input of said differential amplifier and which accepts an input voltage, and a feedback circuit which is interposed between the second input and the output of the differential amplifier so that error characteristics of the feedback circuit are substantially similar to error characteristics of the front end and signal errors introduced by the high impedance front end are canceled by signal errors provided by the feedback circuit. The differential amplifier can be an operational amplifier and the high impedance front ends and the feedback circuits can be source follower FET circuits each having an FET transistor and a resistor connected to the source terminal of said FET transistor. Drains of the source follower FET circuits can be connected at a point, and the amplifier circuit employs a capacitor coupled between the output of the differential amplifier and the point where the drains are connected and a drain resistor, coupled between a positive voltage source for the circuit and the point where the drains are connected.

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First Claim