Question

In solving the problems, assume constant-voltage model for transistors. In case that base-emitter voltage is not specified, use 0.75V for VBEoN of NPN transistors and VEB. oN of PNP transistors. Using the constant voltage model, you will not need to use the given values for L.. Compute the bias point of the circuits depicted in Fig. 5.109. Assume β-100. s 6 x 10-16 A, and VA Hint: you are supposed to find the collector current and to check if the transistors are in forward active region or not Vcc-2.5 V 2

Answer 1

To find thebias point, we need to find region of operation which can be found by finding collector current and voltage across collector and emitter.

To find the bias point, we need to find region of operation which can be found by finding collector current and voltage across collector and emitter. Given data, beta = 100 I_s = 6 times 10^-16 A Required data, I_c = ? Bias point ? KVL in loop (1) -2.5 + 100 I_B + V_BE1 + V_BE2 = 0 -2.5 + 100 I_B + 0.75 + 0.75 = 0 I_B = 2.5 - 1.5/100 I_B = 1/100 I_B = 10 mu A I_C = beta I_B = 100 (1/100) = 1 mA V_C = V_cc - 1 I_C = 2.5 - 1 = 1.5 Volts V_E1 = 0.75 V V_E2 = 0 V V_CE1 = V_C1 - V_E1 = 1.5 - 0.75 = 0.75 volts Hence V_CE1 > 0.2 volts, transistor Q1 is operating in forward active region and the Bias point is given as (I_a, V_CE1) = (1 mA, 0.75 V)

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