Composite complementary symmetrical OTL power amplifier circuit

OTL is the abbreviation of Output Transformer Leas, which means no output transformer . Since the output transformer is eliminated in the circuit, it completely
overcomes the shortcomings of the output transformer itself such as large size, large loss, and poor frequency response, and has been widely used. OTL power amplifier circuits
mainly include complementary symmetrical OTL power amplifier circuits and composite complementary symmetrical OTL power amplifier circuits. Figure 10-12 shows the composite complementary
OTL power amplifier circuit .
    in this circuit. VT1 and Yr2 form a differential input stage voltage amplifier. VT3 is a push tube. VD4 and VD5 are
static bias diodes of the power amplifier output tube. VIb-VT9 constitutes a composite complementary symmetrical OTL circuit and is an output stage circuit. Among them, VT6 and VT7
are two NPN-type composite tubes of the same polarity, which are equivalent to one NPN-type transistor; VT8 and VT9 are PNP-type and NPN-type composite tubes, which are equivalent
to one PNP-type transistor. The
    input signal H is coupled by c1 and then added to the base of VT1. After amplification, it is output from its collector. It is directly coupled to the base of VT3, and
after amplification, it is output from its collector. The positive half-cycle signal output by the collector of VT3 is amplified by VT6 and VT7, and then coupled to SP1 by C7, and
a complete signal is obtained on SP1 .