Question

V = a) *R) V – (1) Vim (1) 3. The difference amp shown in Fig. 3(b) of the lab manual has an output voltage which depends upon the two input voltages according to the equation: R4 (R1+R1 R3+R4 R1 a. Show that when all of the resistors, R1, R3, R4, and Rf are set to 10 kA (as shown in Fig. 3(b)) the output voltage simplifies to Vo = Vp - Vm= e(t). b. Assume that Rf = 10 kN and find the values of the other three resistors such that the output voltage becomes an amplified error signal (V. = Ke*( Vp - Vm) = Kp*e(t)). Ry = 10 ko R1 = R3 = R4 = What values should be used for Kp = 10? Ry = 10 ko R1 = R4 = C. R3 =

Answer 1

a. (1 if all the resistors are equal to 10k, we have CRHAR3 ) = (R+Reflri), and also Rf = Rp. Thus all the resistors Cancel aut each other and vo=vp-vm. b. Assume that tokra 114 Rf inte Here, R3 is an independent variable and the other resistors Rf RI =kp Ri let R3 R4 n. z kp Ykp - RIERE Rz = R3 kp vp-lent) RE). Vm = Kpvp - kpvm. Rf za hi It Kp.) => Itkp = kp takp => ar R4=kp. Rz are Variables. dependent

RL=20=5an Rg = 7502 2 c. For kp = 10 and Rf = lok, We have Ri=Rfkp=1K R3 = 1k , and R4=kp* R3 =lok.