Two Transistor Model of Thyristor

Two transistor model of thyristor is obtained by bisecting the two middle layers along the dotted line in two separate halves as shown in Fig. 1a.

• For a silicon transistor, α is very low at low emitter current I_E.
• The methods of turning ON a thyristor are the methods of making α_1+α_2 to approach to unity.
• Typical variation of current gain with I_E is given in the Fig. 2.