RC T1 RB D. Vin RE iurtor ciecut for preobemns 3 and 3 Assume the following for
ID: 2266680 • Letter: R
Question
RC T1 RB D. Vin RE iurtor ciecut for preobemns 3 and 3 Assume the following for problems 36 and 37. VBE = 0.7 V, VCE 0.2 V hFE = 100 36. (3 pts.) What is the minimum input voltage Vin required to saturate the transistor in the circuit shown in Fig. 11 above? (e) 5.5 V (a) 0 (b) 1.4V (f) 6.7 V (c) 2.0 V () 7.5 V (d) 3.9 V (h) 8.7 V 37. (3 pts) Approximately how much input volt- age Vin would be required to turn on the LED in the circuit shown in Fig. 11 above? (a) 0 (b) 0.2 V (c) 0.7V (d) 0.9 V (e) 1.4 V (f) 2.2 V (g) 2.7 V (h) 2.9 VExplanation / Answer
Answer:-36) At saturation state VCE = 0, So applying KVL in CE part we can werite-
10 - 5IC - 0 - 2 - 5IE = 0 but IC and IE are nearly same, so we get IC = IE = 0.8 mA. Hence voltage drop at emitter is-
VE = 2 + 0.8x5 V = 6V. Thus voltage drop at base = 0.7 + 6 V = 6.7 V. Since base current value is negligible due to very small current flow in base, hence voltage drop in RB is negligible. So Vin = 6.7 V. So option f is correct.
Answer:-37) For LED to glow we need 2V across the LED. But For transistor to be in ON state VBE must be 0.7 V. Hence minimum input voltage required is 2 + 0.7 V = 2.7 V.
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