In electronics, the Sziklai pair, also known as a complementary feedback pair, 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 also called the "complementary Darlington". The configuration is named for George C. Sziklai, thought to be its inventor. Characteristics The current gain of the Sziklai pair is similar to that of a Darlington pair and is the product of the current gains of the two transistors. The figure above illustrates an NPN-PNP pair that acts like a single NPN transistor overall. By replacing Q1 with a PNP transistor and Q2 with an NPN transistor the pair will act like a PNP transistor overall. Applications In a typical application the Sziklai pair acts somewhat like a single transistor with the same type (eg, NPN) as Q1 and with a very high current gain (β). The emitter of Q2 functions as a collector. Hence the emitter of Q2 is labeled "C" in the figure above. Likewise, in a typical application the collector of Q2 (also connected to the emitter of Q1) functions as an emitter and is thus labeled "E". As with a Darlington pair, a resistor (eg, 100 Ω to 1 kΩ) can be connected between Q2's emitter and base to improve its turn-off time (ie, improve its performance for high frequency signals). Advantages One advantage over the Darlington pair is that the base turn-on voltage is only about 0.6 V, or about half of the Darlington's 1.2 V nominal turn-on voltage. Like the Darlington, it can saturate to only about 0.6 V, which is a drawback for high-power stages. Complementary feedback-based output stages Complementary feedback pairs are often used in the output stages of power amplifiers due to their advantages both in linearity and bandwidth when compared with more common Darlington emitter follower output stages. They are especially advantageous in amplifiers where the intended load does not require the use of parallel devices. Complementary feedback pairs can also have the benefit of superior thermal stability under the right conditions. In contrast to the traditional Darlington configuration, quiescent current is much more stable with respect to changes in the temperature of the higher power output transistors vs the lower power drivers. This means that a Sziklai output stage in a class AB amplifier requires only that