phaseinverter

A phase inverter is an electronic circuit that outputs a signal inverted in phase (approximately 180 degrees) with respect to the input. The inverted output is used to drive push-pull power stages or to provide a balanced signal for further processing.

In vacuum-tube amplifiers, a phase inverter provides two signals that drive a pair of output devices so that each half-cycle is amplified by a different tube. The inverter should deliver sufficient gain, a stable phase difference, and similar amplitude of the two outputs to minimize distortion and achieve symmetrical operation.

Common inverter topologies include cathodyne or split-load, which uses a shared load and produces two opposite-phase outputs; concertina, a transformerless scheme based on two triodes that yields closely matched, inverted signals; and the long-tailed pair, a differential arrangement that generates two 180-degree out-of-phase signals with good balance. Each topology has its own trade-offs in terms of bandwidth, output impedance, and drive capability.

In solid-state and digital designs, phase inversion is achieved by inverting amplifiers, differential stages, or DSP processing. The phase-inverted path is used to drive complementary outputs, create balanced lines, or implement feedback networks. While most closely associated with audio tubes, the concept of producing a phase-inverted replica of a signal is applicable wherever two opposite-phase signals are required.

See also: differential amplifier, phase shift, push-pull amplifier.