Phase splitter

Methods

• using a unity gain inverting amplifier to provide an inverted copy of its input signal;
• a split-load amplifier ; a transistor implementation is shown in the diagram;
• a differential pair amplifier can form a phase splitter in two ways:
• * if the shared emitter connection is fed from something approximating a constant current sink then only one input need be driven with signal; the shared connection will vary in voltage with half the amplitude of the input, becoming an input to the second device. The sum of the currents in each of the collectors will be almost constant, hence an increase in one will be matched by an equal decrease in the other, giving rise to equal, but opposite phase, voltages on the outputs. This technique was first described by O.H. Schmitt.
• * if the shared emitter resistor is relatively small, total current will vary with signal, and the signal will not be evenly split across both outputs, so a fraction of the first device's output will have to be fed to the second device's base or grid or gate to balance the amplitudes at the two outputs. Effectively, the second device is acting now as an inverting unity-gain amplifier.
• A transformer with two equal secondary windings can be used.

  Uses

• driving an amplifier in a balanced topology, such as push-pull or H bridge.
• driving balanced transmission lines or balanced audio cables;
• supplying voltages in an oscilloscope to pairs of deflection plates in the CRT;
• producing anti-phase signals used in some filter designs, such as all-pass filters to approximate quadrature signals used in SSB signal generation or old quadraphonic decoders.