(a) For the circuit in Fig. 12.44, show that the loop gain

Chapter 12, Problem 12.71

(choose chapter or problem)

(a) For the circuit in Fig. 12.44, show that the loop gain of the common-mode feedback loop is Recall that the CMF circuit realizes the transfer characteristic . Ignore the loading effect of the CMF circuit on the collectors of the cascode transistors. (b) For the values in Example 12.6, calculate the loop gain . (c) In Example 12.6, we found that with the CMF absent, a current mismatch A gives rise to V. Now, with the CMF present, use the value of loop gain found in (b) to calculate the expected and compare to the value found by a different approach in Example 12.6. [Hint: Recall that negative feedback reduces change by a factor equal to