The source follower uses local series-shunt feedback to achieve a low output resistance Ro. This resistance can be lowered further if we apply additional negative feedback, in the manner depicted in...

The source follower uses local series-shunt feedback to achieve a low output resistance Ro. This resistance can be lowered further if we apply additional negative feedback, in the manner depicted in Fig. P7.21. In this circuit, aptly known as super source follower, M1 is the source follower proper, and M2 provides additional feedback around M1. Using the series-shunt procedure, estimate Ro, and verify that the presence of M2 lowers the output resistance 1ygm1 approximately by the factor gm2ro1. Hence, calculate Ro if both FETs have gm 5 1 mA/V and ro 5 25 kV. How does the present procedure handle the contribution from gmb1? Explain!