Wide bandwidth CMOS class A amplifier

摘要

A CMOS inverter is coupled to drive a bipolar transistor emitter follower which has a field effect transistor load. The load transistor is provided with a d-c bias that causes the circuit to function as a class A amplifier. The amplifier has a gain-band-width product that is much higher than can be achieved with CMOS inverters alone and such amplifiers can be cascaded to achieve extremely high gain values. It is preferred to obtain the required class A bias from a similar circuit wherein the load transistor is replaced by a resistor and the emitter follower has its output directly coupled to the CMOS inverter input. This means that the voltage across the resistor is that value that will operate the bias circuit at its trip point independent of the manufacturing variables that affect transistor threshold values. This amplifier configuration is useful in constructing high-speed, high-sensitivity clocked comparators and clocked latches.