Question

For the system shown, find the equivalent resistance Req = Vx/lx in both cases. A. Suppose that the black box is an amplifier of ideal transconductance with a short circuit transconductance of -0.2S. B. The black box is an amplifier with an entrance resistance of 20 kOhm, an exit resistance of 25 kOhm and a short circuit transconductance of 0.2S. Ix Vx + + Vin Vo

Answer 1

SOLUTION Pager: CONDITIONI: : for the given system, Vin=va Ve Ai + + Vin for an Ideal trans conductance amplifier, I. Im Vin * gm Trans conductance The Principle of Trans conductance Amplifier Convert Enput Voltage to output Current. so for the above System, is to Pae: -Po Ти ) v u + 1 Vin € 0.25) Vin For the given system, (x==(-0.29) Vin [i from Trans Conductance Ix=0.2 xVx Amplified poinciple [: Vaz Va = vin Pe = 0.25 Vx

Equivalent Resistance, Page 2 Reqa Vne Ix Req 10 . 0.2 10 h Req=5 ohm * For a Cincuit 2 -0.25, tuan & concluchance the equivalent Resistance obtained is Req=502 CONDITION 2: Given, Entrance Resistance, Rin - 2012 Exit Resistance, Rout = 25K9 Птаав Солии Crance, 0.25 lu 0 CO Vr va + Vin 20K 2 (025)Vin 25 KS2 on Applying KCL at Node 1: Vin va Ixt 0.25 Vin По К 25 K for the given Vin=vm ale have System.

Page 3: 0.2 Ure & Pr 20 25 Vrex 5+4 0.avre + In 100K quae = zövre + look Is - Ia x 100 Ks (20,000 - 9) va 5 10 Vx In 199.97 Vie Ix -552 Real for a trans conductance, 9 m=0.as with Rin=20kh and Rout Rout - 25K2, the 06tafred Equivalent resistance, Req: -552