electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

, the Sziklai pair, also known as a complementary feedback pair, is a configuration of two

bipolar transistor A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipola ...

s, similar to a

Darlington pair In electronics, a multi-transistor configuration called the Darlington configuration (commonly called a Darlington pair) is a circuit consisting of two bipolar transistors with the emitter of one transistor connected to the base of the other, su ...

. 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 A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias activ ...

(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