Distributed amplifier

Abstract

A distributed amplifier having a plurality of successively coupled field effect transistors with cascaded gate electrodes and cascaded drain electrodes. A first one of such transistors has the gate electrode thereof coupled to an input terminal adapted to receive an input radio frequency signal and the drain electrode thereof coupled to a dc drain electrode bias circuit. The last one of the successively coupled field effect transistors has the gate electrode thereof coupled to a dc gate electrode bias circuit and a drain electrode coupled to a radio frequency output terminal which produces an amplified radio frequency signal. The source electrodes of the plurality of transistors are coupled to ground. A drain bias voltage source is coupled between ground and the drain electrode bias circuit, such bias circuit providing a direct current path between such drain bias voltage source and the drain electrodes of the transistors. The drain electrode dc bias circuit has a complex impedance with the real component thereof being provided, in part, by a resistor in such bias circuit. The resistor is coupled in series with a grounded high frequency by-pass capacitor and, hence, is not in the direct current path between the drain bias voltage source and the drain electrodes, but rather is in the radio frequency signal path to ground. With such arrangement, only a relatively small amount of dc power is dissipated by the resistor in such drain biasing circuit.