Sziklai Pair

In electronics, the Sziklai pair (also known as a "compound transistor") is a configuration of two bipolar transistors, similar to a Darlington pair. In contrast to the Darlington arrangement, the Sziklai pair has one NPN and one PNP transistor, and so it is sometimes called the "complementary Darlington". Current gain is similar to that of a Darlington pair, which is the product of the gains of the two transistors. The configuration is named for its inventor George C. Sziklai.

One advantage over the Darlington pair is that the base turn-on voltage is only about 0.6V or half of the Darlington's 1.2V nominal turn-on voltage. Like the Darlington, it can saturate only to 0.6V, which is a drawback for high-power stages.

As with a Darlington pair, a resistor (e.g., 100Ω–1kΩ) is usually connected between Q2 emitter and base to improve its turn-off time (i.e., its performance for high frequency signals).