Fully differential amplifier circuit with high accuracy and high dynamic range

Abstract

The invention discloses a fully differential amplifier circuit with high accuracy and a high dynamic range. The overall circuit mainly comprises an operational amplifier input grade, an operational amplifier middle grade, an operational amplifier output grade and a common-mode feedback module and belongs to the field of integrated circuits. In order to improve the accuracy and the dynamic performance of the circuit, the circuit is combined with a folding type cascode operational amplifier structure adopting a chopper technique and an AB type push-pull structure; however, the AB type push-pull circuit requires a floating voltage source to provide static polarization, the cascading number of cascode circuits is increased, and the voltage margin is limited; besides, even if all MOS (metal oxide semiconductor) transistors in the cascode circuits are modulated to the normal work zone, the work sections of the cascode circuits are very limited, and the robustness of the circuit is easily affected by transient pulse and PVT change; the cascode type current source of the cascode grade is changed into a two-transistor self-cascading type current source in order to solve the problem, and the voltage margin of the circuit is improved while the circuit accuracy is guaranteed.

Description

technical field [0001] The invention relates to a full differential amplifier circuit, in particular to a full differential amplifier circuit with high precision and high dynamic range, belonging to the field of integrated circuits. Background technique [0002] The fully differential amplifier circuit is a circuit structure of differential input and differential output. Since the currents of the P-type MOS transistor and the N-type MOS transistor cannot be perfectly matched, it is easy to cause the output common mode level to shift, so the fully differential amplifier needs a common mode. The feedback module is used to stabilize the output common mode level; although the full differential amplifier increases the power consumption compared with the single-ended output amplifier, it improves the common mode rejection ratio (CMRR) and the output voltage swing, which is more suitable for some high precision and high linearity applications. degree of occasion. [0003] Specific...

AI Technical Summary

Problems solved by technology

However, since Class AB push-pull circuits require floating voltage source biasing, this results in limited voltage margin when combined with traditional folded cascode amplifiers with chopping techniques

In addition, even if each MOS tube is adjusted to the normal working area, due to the relatively limited working range of the tube, it is very susceptible to the influence of voltage spikes caused by chopper switch switching or other factors, such as: cascode current mirror of a tube The drain terminal voltage can only be in the saturation region in a certain limit range. An instantaneous pulse causes the drain terminal voltage of the tube to jump out of this limit range, causing the tube to work abnormally, which in turn causes the current mismatch of the current mirror, and finally reduces the circuit accuracy; Moreover, to restore the working area of ​​the tube to normal, it is limited by the settling time of the amplifier, which indirectly weakens the speed of the entire amplifier circuit.

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