Multistage amplifier

Abstract

The invention discloses a multistage amplifier which comprises a differential input stage, at least one intermediate amplification stage and an output stage. The differential input stage, the intermediate amplification stages and the output stage are sequentially in cascade connection with one another; the differential input stage comprises a first MOS (metal oxide semiconductor) transistor, a second MOS transistors, a third MOS transistor, a fourth MOS transistor, a first current mirror circuit, a second current mirror circuit, a first bias circuit and a first load circuit, source electrodes and grid electrodes of the first MOS transistor and the second MOS transistor are coupled with one another, and first voltages can be received by the grid electrodes of the first MOS transistor and the second MOS transistor; source electrodes and grid electrodes of the third MOS transistor and the fourth MOS transistor are coupled with one another, second voltages can be received by the grid electrodes of the third MOS transistor and the fourth MOS transistor, the source electrodes of the third MOS transistor and the second MOS transistor are coupled with each other, and first bias currents can be received by the source electrodes of the third MOS transistor and the second MOS transistor; a common grid electrode of the first current mirror circuit is coupled with a drain electrode of the third MOS transistor, and a first drain electrode of the first current mirror circuit is coupled with a drain electrode of the first MOS transistor; a common grid electrode of the second current mirror circuit is coupled with a drain electrode of the second MOS transistor, and a first drain electrode of the second current mirror circuit is coupled with a drain electrode of the fourth MOS transistor; the first bias circuit is suitable for providing bias circuits for the first current mirror circuit and the second current mirror circuit; the first load circuit is suitable for providing load for the differential input stage. According to the scheme, the multistage amplifier has the advantages of high gain and wide unity gain bandwidth.

Description

technical field [0001] The invention relates to the field of analog circuit design, in particular to a multi-stage amplifier. Background technique [0002] Operational amplifier (hereinafter referred to as amplifier) ​​is a basic device of analog integrated circuit. The application requirements for amplifiers are generally high gain, high bandwidth, and high slew rate. [0003] For example, a typical multi-stage amplifier in the prior art may include a differential input stage, at least one intermediate amplifier stage, and an output stage; wherein, optionally, the differential input stage may adopt a cascode structure, and may include four MOS The current mirror load contained in it can convert the differential signal into a single-ended signal and output it; the intermediate amplifier stage can be a common source structure, and further amplify the single-ended signal output by the differential input stage; the The output stage is adapted to improve the load carrying capa...

AI Technical Summary

Problems solved by technology

However, as the process size continues to shrink, the supply voltage of the amplifier continues to decrease, which reduces the gain and output swing of the amplifier, which in turn reduces the gain bandwidth of the amplifier

In the prior art, the above-mentioned problems are usually solved by increasing the number of amplifier stages, but this will lead to a larger circuit scale and a complicated circuit structure.

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