Open-loop amplifier with stable output common-mode voltage

Abstract

The invention relates to an open loop amplifier with stable output common-mode voltage. The open loop amplifier comprises a main amplifier unit and an auxiliary amplifier unit. Compared with a conventional negative feedback amplifier with stable output common-mode voltage, the open loop amplifier has the beneficial effects that the differential output common-mode voltage of the main amplifier unit under an open loop structure is stable; the differential output end of the main amplifier unit does not adopt a common-mode feedback circuit, so that the output load is lowered, the working conversion speed of the amplifier is increased, and the frequency of an analog input signal can exceed 1GHz when the dynamic indicator SFDR (Spurious Free Dynamic Range) of the main amplifier unit exceeds 70dB. The circuit provided by the invention is applied to the field of ultrahigh-speed sampling / retaining circuits in low-voltage CMOS (Complementary Metal-Oxide-Semiconductor Transistor) process circuits with a high dynamic performance requirement.

Description

technical field [0001] The invention relates to an open-loop amplifier with stable output common-mode voltage, in particular to an amplifier with stable output common-mode voltage in an open-loop state. It is directly applied in the field of ultra-high-speed sampling / holding circuits in low-voltage CMOS process circuits that require high dynamic performance in integrated circuits. Background technique [0002] At present, as the sampling rate of the A / D converter breaks through the GSPS order of magnitude, the working frequency of the front-end sample / hold circuit is also required to increase, not only requiring the sampling rate to exceed the GSPS, but also ensuring that the dynamic performance meets the requirements of the ADC. / Hold the amplifier in the circuit to put forward higher requirements. [0003] Conventional output common-mode voltage stabilized negative feedback amplifiers such as figure 1 shown. In this negative feedback amplifier, NMOS transistors M1, M2, ...

AI Technical Summary

Problems solved by technology

[0004] In order to overcome the problem of low conversion speed of the conventional negative feedback amplifier with stable output common-mode voltage, the present invention proposes an open-loop amplifier with stable output common-mode voltage, which can not only control the output common-mode voltage of the amplifier well, but also Does not affect the working switching speed of the amplifier

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