Sziklai pair

In a typical application the Sziklai pair acts somewhat like a single transistor with the same type (e.g., NPN) as Q1 but with a very high current gain (β).

This potentially simplifies the design and implementation of a stable class AB amplifier, reducing the need for emitter resistors.

Alternately, if a germanium PNP device was used, it would have significantly different characteristics than the silicon NPN transistor.

In the quasi-complementary topology, the performance of the lower pull pair, which uses a single NPN transistor, more closely matches the performance of the upper push pair, which consists of two NPN transistors and an identical power device.

[3] For decades the quasi-complementary output stage made sense; but because PNP and NPN power transistors are now equally available and have more closely matched performance characteristics, modern audio power amplifiers often use equivalent topologies for both pairs: either 2 Darlingtons or 2 Sziklai pairs.