Power amplification circuit

摘要

Variations in the waveform of high-frequency signals amplified by a field-effect transistor (FET) in a power amplification circuit due to changes in temperature are reduced. A FET having an n-type active layer, a source electrode, a drain electrode and a gate electrode is formed on a (1 0 0)-crystal plane of a semi-insulating GaAs substrate. The FET is protected by a passivation film. The angle &thetas;, formed between the longitudinal axial direction of the gate electrode and the &lang&0 -1 -1&rang&-direction, is set at an angle of from 0 DEG to 90 DEG corresponding to the impurity concentration of the n-type active layer, in order that the temperature coefficient of the FET threshold voltage becomes substantially equal to the temperature coefficient of the gate bias voltage applied from a power supply to the gate electrode. If the angle &thetas; is set at 45 DEG , then the temperature coefficient of the FET threshold voltage becomes zero. <IMAGE>