Body Biasing Device and Operational Amplifier thereof

An operational amplifier, comprising:

• an output stage circuit for receiving a differential output signal pair and accordingly outputting an output signal at an output node;
• a P-type differential pair for receiving a differential input signal pair and accordingly outputting the differential output signal pair, comprising:
• a first P-type transistor comprising a gate coupled to a first differential input, a source coupled to a current source, a drain coupled to the output stage circuit, and a body coupled to a body bias;
• and
• a second P-type transistor comprising a gate coupled to a second differential input, a source coupled to the current source, a drain coupled to the output stage circuit, and a body coupled to the body bias;
• and
• a body biasing device comprising:
• a detection unit for detecting a detected voltage related to the differential input signal pair to output a control signal;
• and
• a selection unit coupled to the detection unit for outputting the body bias according to the control signal.