Operational amplifier having DC offset cancellation capability
View Patent ↗An operational amplifier includes an input stage for generating a first differential output signal pair according to a first differential input signal pair, an output stage for generating a second differential output signal pair according to at least a second differential input signal pair, and a high-pass filtering circuit coupled between the input stage and the output stage for performing high-pass filtering on the first differential output signal pair, for generating the at least a second differential input signal pair.
1. An operational amplifier comprising:
an input stage for generating a first differential output signal pair according to a first differential input signal pair;
an output stage for generating a second differential output signal pair according to at least a second differential input signal pair; and
a high-pass filtering circuit coupled between the input stage and the output stage for performing high-pass filtering on the first differential output signal pair, for generating the at least a second differential input signal pair;
wherein the high-pass filtering circuit is coupled to at least one bias voltage, each bias voltage is a common mode voltage of one of the at least a second differential input signal pair, and the output stage comprises a common mode feedback circuit for generating one of the at least one bias voltage.
2. The operational amplifier of claim 1 , wherein the high-pass filtering circuit comprises a plurality of high-pass filtering units, each high-pass filtering unit being coupled to one of a plurality of output terminals of the input stage, one of a plurality of input terminals of the output stage, and a bias voltage.
3. The operational amplifier of claim 1 , wherein the high-pass filtering circuit comprises a plurality of high-pass filtering units, each high-pass filtering unit comprising:
a capacitor coupled between one of a plurality of output terminals of the input stage and one of a plurality of input terminals of the output stage; and
a resistive component coupled between the output terminal and a bias voltage which is a common mode voltage of one of the at least a second differential input signal pair.
4. The operational amplifier of claim 3 , wherein the resistive component is a resistor.
5. The operational amplifier of claim 3 , wherein the resistive component is a metal-oxide-semiconductor field effect transistor.