Low noise detector amplifier

Claim 1

A signal translating circuit responsive to wave energy signals comprising: a pair of field-effect semiconductor devices each having a gate, drain and source electrode, input means coupled to the source and gate of one of said devices, said input means including a transducer generating an electrical current in response to receipt of said wave energy and an impedance coupled to receive said electrical current from said transducer, said transducer exhibiting capacitance to said source and gate electrodes of said one device, the source electrode of said one of said devices being coupled to the gate electrode of the other of said devices to provide a positive feedback path whereby an electrical potential at said source of said one device is substantially the same as the electrical potential at said gate of said other device, the drain of said one device being connected to said source of said other device, each of said devices being operated unconditionally stable at a gain closely approaching but less than unity by coupling the source electrode of said one device to a supply of substantially constant current, wherein, in response to said wave energy the difference in electrical potential between said source and gate electrodes and said gate and said drain electrodes of said one device respectively is substantially zero, to thereby substantially reduce the input capacitance between said source and said gate electrode and the stray capacitance between said gate and drain electrode of said one device.