Experiment 10 - Base-Emitter Voltage of the Sziklai Pair

The Sziklai pair has a big advantage over the Darlington pair. With the same gain, the base-emitter voltage is only half as large.

Measuring the voltage UBE of a Sziklai pair. (Enlarge) Consider the circuit shown. Turning the potentiometer P1 until the Sziklai pair is saturated, you measure a base-emitter voltage of... UBE = 0.65 V

Circuit diagram measuring the voltage UBE of a Sziklai pair.

This value is identical to that of a single transistor. This is an advantage over the Darlington pair.

Despite this advantage, there are no ready-made Sziklai pair transistors. This is due to the manufacturing process of transistors.

The shown Sziklai pair behaves like a NPN transistor. However you can modify the circuit in order to get a PNP Sziklai pair...