The negative-feedback loop of Fig. P7.55 is made up of a ring of three CMOS inverters. Assume the FETs have gmn 5 gmp 5 1 mA/V and ron 5 rop 5 30 kV, and the stray capacitances of each inverter can be...

The negative-feedback loop of Fig. P7.55 is made up of a ring of three CMOS inverters. Assume the FETs have gmn 5 gmp 5 1 mA/V and ron 5 rop 5 30 kV, and the stray capacitances of each inverter can be modeled by a single equivalent capacitance Co 5 1 pF from the output node to ground. (a) Obtain an expression for T(jf), fi nd fx, x, and m, and verify that the loop is unstable, this being the reason why the circuit is called a ring oscillator. (b) Find an external shunt capacitance Cshunt that, when connected between the output terminal and ground of any one of the inverters will stabilize the loop for m 5 458.