Subject: CMOS VLSI Design

Topic: MOS Operational Amplifiers

Difficulty: High

Gain Boosted opamp:

i) Single stage cascode opamp have limited gain.
ii) 2-Stage opamp high gain at high speed.
iii) Gain boosted high gain at high speed.
iv) To increases gain, basic idea is to increase output impedance further w/o increase number of devices.

v) Thus gain can be "boosted" substantially without stacking more cascode devices on top of $M_2$. The cascode opamp with gain boosted approach is shown below: