Question

Example 5.21 The circuit of Fig. 5.29 is biased with a collector current of 1 mA and Rc = 1 kQ. If B 100 and VA 10 V, determine the small-signal voltage gain and the I/O impedances. Solution We have (5.135) VT = (26 Ω)-1 (5.136) and (5.137) Ic = 10 kΩ (5.138) Thus, (5.139) (5.140) A,--g,n(Rellro) 35 (As a comparison, if Vl 00, then Au #38.) For the 1/0 impedances, we write (5.141) (5.142) (5.143) gm = 2.6 kΩ and Rout Rcllro (5.144) = 0.91 kΩ (5.145) Exercise Calculate the gain if V-5V

For Exercise, V_A=5V

Answer 1

g_m = I_c/V_T g_m = (26 Ohm^-1) r_0 = V_A/I_C = 5/1 times 10^-3 r_0 = 5 K Ohm A_v = -g_m (R_c Vertical-bar Vertical-bar r_0) = -26 times (R_c Vertical-bar Vertical-bar r_0) = -26 times 0.83 A_V = -21.66 R_in = r_ = beta/g_m = 100/26 = 2.6 k Ohm R_out = R_c Vertical-bar Vertical-bar r_0 R_out = 0.83 k Ohm