The DC power applied to a transistor allowing it to operate as an active amplifying or signal generating device. Typical voltage levels in GaAs FETs used in receivers are 1 to 7 volts between the drain and source terminals, and 0 to −5 volts on, or between, the gate and source terminals. For microwave systems, DC voltages and currents, provided by batteries or AC/DC converters required to “bias” transistors to a region of operation where they will either amplify, mix or frequency translate, or generate (oscillators) microwave energy. Since energy can be neither created nor destroyed, microwave energy amplification or creation is accomplished at the expense of DC energy.
Input bias current and input offset current also affect the net offset voltage seen for a given amplifier. The voltage offset due to these currents, however, are separate from the input offset voltage parameter and is related to the impedance of the signal source and of the feedback and input impedance networks such as the two resistors used in the basic inverting and non-inverting amplifier configurations.