darlington pair การใช้

Another drawback of the Darlington pair is its increased " saturation " voltage.
The Darlington pair has more phase shift at high frequencies than a single transistor and hence can more easily become unstable with negative feedback ( i . e ., systems that use this configuration can have poor phase margin due to the extra transistor delay ).
Darlington pairs are available as integrated packages or can be made from two discrete transistors; Q 1 ( the left-hand transistor in the diagram ) can be a low power type, but normally Q 2 ( on the right ) will need to be high power.
Likewise, in a typical application the collector of Q2 ( also connected to the emitter of Q1 ) plays the role of an emitter and is thus labeled " E . " As with a Darlington pair, a resistor ( e . g ., 100? & ndash; 1k? ) is usually connected between Q2's emitter and base to improve its turn-off time ( i . e ., its performance for high frequency signals ).