(a) A student is trying to use a voltage comparator as a unity-gain buffer (v 5 1). If the comparator has a dc gain of 104 V/V and three pole frequencies at 1 MHz, 20 MHz, and 50 MHz, fi nd fx , x ,...

(a) A student is trying to use a voltage comparator as a unity-gain buffer (v 5 1). If the comparator has a dc gain of 104 V/V and three pole frequencies at 1 MHz, 20 MHz, and 50 MHz, fi nd fx , x , and m, and verify that the circuit is unstable. (b) Comparators do not have on-chip compensation because they are meant for open-loop operation. However, the user can still stabilize a negative-feedback comparator by creating an additional pole fD off-chip, and letting the loop gain be dominated by this new pole. In Fig. P7.58 this pole is established via the feedback factor by means of shunt capacitance Cshunt, which results in v( jf ) 5 VnyVo 5 1y(1 1 jfyfD), fD 51y(2RCshunt). (a) Find fD for m 5 608. Hence, assuming R 5 30 kV, fi nd the required value of Cshunt. What is the expression for T( jf ) after compensation?