3. Contoso
S u i t e s
3
Electronics :-
▪ DIAC
▪ The Diac is a two-junction bidirectional semiconductor device designed to break
down when the AC voltage across it exceeds a certain level passing current in either
direction
4. Contoso
S u i t e s
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Electronics :-
▪ Thyristor
▪ Two layer ( P-N )
▪ Multi-layer semiconductor device
▪ Two transistors connected back-to-back
▪ The thyristor is a three-terminal device labelled
“Anode”, “Cathode” and “Gate”
▪ Current operated devices, a small Gate current controls
a larger Anode current.
▪ Acts like a controlled rectifying diode
▪ Power semiconductor devices
▪ Anode current must be greater than holding current
to maintain conduction
Turn off when the load current falls virtually to
zero, or the thyristor is reverse biased
5. Contoso
S u i t e s
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Electronics :-
▪ Thyristor
Natural Commutation
Forced Commutation
▪ Anode, (A) is positive with respect to the Cathode, (K), for regenerative
latching to occur
▪ Inject a small trigger pulse of current (not a continuous current) into the
Gate
