1. Field of the Invention
The present invention relates to a differential amplifying circuit suitable for an integrated circuit.
2. Description of the Related Art
For example, to realize a high-precision pipelined A/D converter, a differential amplifying circuit with a high differential DC gain (hereinafter expressed as “DC gain”) is needed. One of configurations to obtain a high DC gain in the differential amplifying circuit is a configuration including a gain boost amplifying circuit. The DC gain of the differential amplifying circuit can be increased by a DC gain of the added gain boost amplifying circuit. As an example of an A/D converter using the differential amplifying circuit including the gain boost amplifying circuit, there is one disclosed in the following related art 1.
A gain boost amplifying circuit disclosed in this related art has a configuration in which a transistor is added to adjust the output common mode voltage to a vicinity of a median value between reference electric potentials vdd and vss (hereinafter expressed as “reference potentials vdd and vss”), and power consumption increases by an amount corresponding to a current flowing through this transistor.
[Related Art 1] Yun Chiu et al., “A 14-b 12-MS/s CMOS pipeline ADC with over 100-dB SFDR”, IEEE Journal of Solid-State Circuit, United States, IEEE, December 2004, Vol. 39, No. 12, pp. 2139-2151