In the common base amplifier, when the input and output signals are compared:

In a common base amplifier, the input signal is applied to the emitter terminal and the output is taken from the collector terminal. When the input emitter voltage increases, it causes a decrease in the forward bias of the emitter-base junction, which lowers the collector current and subsequently increases the output voltage. Because a positive-going input signal directly results in a positive-going output signal, the input and output waveforms follow each other perfectly. Therefore, there is no phase inversion; the signals remain completely in phase (0 degrees apart). Distractors mentioning a 180-degree phase shift apply to the common emitter configuration. Options suggesting 90-degree phase shifts are characteristic of purely reactive circuits (capacitors and inductors), not standard resistive transistor amplifiers.