Cmos class ab operational amplifier operating from a single 1.5v cell

An operational amplifier utilizing a single 1.5V power supply, comprising:

• a voltage supply;
• transistors biased in their sub-threshold, also called weak inversion, region of operation;
• a class AB control circuit having a plus and minus input with a rail-to-rail common mode swing, a current source input, said control circuit delivering an amplified input signal to a class AB output stage, said control circuit comprising p-channel and n-channel transistors;
• said class AB output stage with inputs and an output, said inputs of said output stage connected to said control circuit, said output of said output stage delivering current to drive an external load, said output stage comprising a p-channel and n-channel output transistor, said transistors of said output stage moving from weak inversion in a quiescent state to strong inversion when delivering high currents to said external load;
• and
• an internal feedback circuit connected to said control circuit, said internal feedback circuit setting up DC voltages for said control circuit to maintain quiescent currents at a small known value in said output transistors of said output stage, said internal feedback circuit comprising p-channel and n-channel transistors.

An operational amplifier utilizing a single 1.5V power supply, comprising:

• a voltage rail vdd;
• a reference rail vss;
• transistors biased in their sub-threshold, also called weak inversion, region of operation;
• a class AB control circuit having a differential input and applying an input signal with a rail-to-rail common mode swing to that differential input, a current source input, said control circuit delivering an amplified input signal to a class AB output stage, said control circuit comprising a plurality of p-channel and n-channel transistors, and said control circuit connected to said voltage rail vdd and said reference rail vss;
• said class AB output stage with inputs and an output, said inputs of said output stage connected to said control circuit, said output of said output stage delivering current to drive an external load, said output stage comprising a p-channel and n-channel output transistor, a resistor and a first, a second, and a third capacitor, said output stage connected to said voltage rail vdd and said reference rail vss, said transistors of said output stage moving from weak inversion in a quiescent state to strong inversion when delivering high currents to said external load;
• and
• an internal feedback circuit connected to said control circuit, said internal feedback circuit setting up DC voltages for said control circuit to maintain quiescent currents at a small known value in said output transistors of said output stage, said internal feedback circuit comprising a plurality of p-channel and n-channel transistors, and said internal feedback circuit connected to said voltage rail vdd and said reference rail vss.