bias (in electricity)
bias, a voltage, current, or other input applied to a device or system as a reference or to set its conditions of operation. A bias is usually steady but may vary with time, usually within a fixed and known range and with a fixed and known frequency. In electronics, the most common forms of bias are the voltage applied to the grid of an electron tube to set its operating conditions and the current applied to the base of a transistor to perform the same function. In tape recording, a bias current, usually alternating with a frequency in the ultrasonic range, is mixed with the signal to be recorded to minimize distortion produced by the tape itself.