Chapter 15, Problem 15.13TYU

(a) Consider the bridge amplifier in Figure 15.46 with parameters $R_1=R_3=20\text{k}\Omega$ , $R_2=40\text{k}\Omega$ , $R_4=60\text{k}\Omega$ , and $R_L=500\Omega$ . Assume the op−amps are biased at ± 15 V and the peak output voltage of each op−amp is limited to ±12V. Determine (i) the voltage gain of each op−amp circuit, (ii) the average powerthat can be delivered to the load, and (iii) the peak amplitude of the input voltage ${\upsilon }_I$ .(b) From the results of part (a), change the values of $R_2$ and $R_4$ such that the same average power is delivered to the load but the magnitude of the required input voltageis cut in half. What are the required amplifier gains? (Ans. (a) (i) $A_{\upsilon 1}=+3$ , $A_{\upsilon 2}=-3$ , (ii) ${\bar{P}}_L=0.576\text{W}$ , (iii) ${\upsilon }_I=4\text{V}$ ; (b) $R_2=100\text{k}\Omega$ , $R_4=120\text{k}\Omega$ , $A_{\upsilon 1}=+6$ , $A_{\upsilon 2}=-6$ )