Fet differential amplifier

Claim 1

In a differential amplifier having a power source of positive and negative voltages including a pair of field effect transistors of generally similar characteristics as active input elements, the improvements for equalizing differences between said transistors and stabilizing amplifier operation, comprising a differentially adjustable load in the output circuit of each of said transistors whereby an increase in the load of one of said transistors simultaneously reduces the load of the other of said transistors; a signal source connected to the input to one of said transistors; an adjustable virtual ground connected to the input of the other of said transistors; said virtual ground including a voltage divider connected across said positive and negative voltage source and an adjustable terminal on said divider positioned near the point on said divider possessing 0 electrical potential; and a third field effect transistor having characteristics generally similar to said pair of transistors and having source, drain and gate electrodes, said source and drain electrodes being connected together and to the input of one of said pair of transistors, and means for adjustably biasing said gate electrode whereby said third transistor provides a source of current responsive to ambient temperature variations to compensate for amplifier gain variations.