The transistor amplifier configuration which produces a 180° out of phase output from the input signal is the common?

The common emitter configuration of a transistor amplifier is characterized by producing an output signal that is inverted, meaning it is 180° out of phase with the input signal. This is due to the operation of the transistor in this configuration, where a small change in the input voltage at the base leads to a larger change in the output voltage at the collector. The phase inversion occurs because an increase in input voltage drives the transistor into a more conductive state, which decreases the voltage at the collector. Hence, when the input signal goes positive, the output goes negative, resulting in the out-of-phase relationship.

This configuration is widely utilized in amplifier circuits for its ability to provide voltage gain along with the phase inversion. In contrast, the other configurations like common collector and common base do not produce this 180° phase shift in the output with respect to the input signal. Thus, understanding the phase relationship in various transistor configurations allows technicians to select the appropriate circuit topology based on the desired output characteristics.