1-29
Figure 1-28.—Two-stage transistor phase splitter.
Q-29. What is a phase splitter?
PUSH-PULL AMPLIFIERS
One use of phase splitters is to provide input signals to a single-stage amplifier that uses two
transistors. These transistors are configured in such a way that the two outputs, 180º out of phase with
each other, combine. This allows more gain than one transistor could supply by itself. This "push-pull"
amplifier is used where high power output and good fidelity are needed: receiver output stages, public
address amplifiers, and AM modulators, for example.
The circuit shown in figure 1-29 is a class A transistor push-pull amplifier, but class AB or class B
operations can be used. Class operations were discussed in an earlier topic. The phase splitter for this
amplifier is the transformer T1, although one of the phase splitters shown earlier in this topic could be
used. R1 provides the proper bias for Q1 and Q2. The tapped secondary of T1 develops the two input
signals for the bases of Q1 and Q2. Half of the original input signal will be amplified by Q-1, the other
half by Q-2. T2 combines (couples) the amplified output signal to the speaker and provides impedance
matching.
Figure 1-29.—Class A transistor push-pull amplifier.
