Differential amplifying circuit and multi-stage differential amplifying circuit using the same

A multi-stage differential amplifying circuit, comprising:

• a first differential amplifying circuit coupled to receive an input signal at first and second input terminals and provides a differential output signal at a forward and a reverse output terminal, the first differential amplifying circuit includes a first input transistor having a gate coupled to the first input terminal and a second input transistor having a gate coupled to the second input terminal;
• a current source coupled between a first power supply and a current supply node and the current supply node provides current to the first and second input transistors;
• an amplitude controlling transistor having a gate coupled to the current supply node and providing a controllable impedance path between the forward and a reverse output terminals;
• and
• a second differential amplifying circuit coupled to receive the differential output signal and provide a multi-stage output signal.

A differential amplifying circuit, comprising:

• first and second input terminals,
• a first differential amplifying circuit coupled to receive a differential input signal from the first and second input terminals and provide a differential output signal at a forward and a reverse output terminal;
• and
• an amplitude controlling insulated gate field effect transistor (IGFET) providing a controllable impedance path between the forward and reverse output terminals wherein
• a potential at a control gate of the amplitude controlling IGFET varies as an offset voltage of the differential input signal varies.