Question

The IV characteristic of a SCR is shown in Fig. 4a, and a SCR circuit is shown in Fig. 4b. lo (mA) 12 10 8 La - OA 6 4 Vcc (V) 100 120 140 160 180 20 40 60 80 Fig. 4a Voc 302 1002 VAK Vio Vo = 0.7V 1 OV Fig. 4b (a) Find the holding current IH. (b) Given that the supply voltage Vcc is 80V, the gate trigger current IGT is 12mA, calculate the minimum input voltage Vin required to turn the SCR on. (c) If Vak is 2V when the SCR is turned on, determine the value of Voc below which the conducting SCR is turned off. (d) Can a conducting SCR be turned off by reducing the gate voltage VG to OV?

Answer 1

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Given ovec 17. (mA) 30kr î 12 Loor 2 →19 IG=0A VAK IH 76 Vin VGE OV 40 160 + vcc(v) ao the ② Holding йиши lussent which must when in order to хемоли in the one state. cinuit Current :- Pass through SCR from IH ID Veure vec plot so awarding 6 MA Vin min = ? to Vecs 80 V IGT = 12mA Tum on SCR : VG from cixcuit Apply kul vinmin 4 (140) = Vin win 12 x 20-3 x 10 0.7 a Vinnin 0.7 + 1.2 1.9 valt Vin nina dog volt below which @ it VAK - 2V, conducting SCR SON What is Ice Turned OFF. So which went below SER SCR OFF 6 mA. in outer loop Now Apply Ken Vee - 10x30 - VAKO 6x103 x 30 +2 25 Vce z Vcc = .18 +2 =) Vce = 2018 valt signal loses A Conduting SCR - when once ser conduling the gate all control due to lacking action so after gate signal will not affect SCR SIR by reduing gate voltage so we Condution SER Turned OFF the connat OV.