A Push-Pull Operational Amplifier with Feedforward Compensation

Abstract

The present invention discloses a feedforward compensation push-pull operational amplifier. The feedforward compensation push-pull operational amplifier includes a differential first gain stage circuit, a differential second gain stage circuit, and a feedforward frequency compensation circuit of a push-pull structure. The differential first gain stage circuit and the differential second gain stage circuit are connected in series and then are parallelly connected with the feedforward frequency compensation circuit of the push-pull structure. The feedforward frequency compensation circuit of the push-pull structure consists of a P-channel metal oxide semiconductor (PMOS) transistor M1a and an N-channel metal oxide semiconductor (NMOS) transistor M1b of the push-pull structures, a PMOS transistor M2a and an NMOS transistor M2b of the push-pull structures, and an NMOS transistor M3 providing a tail current. In the feedforward compensation push-pull operational amplifier, the feedforward frequency compensation circuit of the push-pull structure is adopted to replace a traditional pole-splitting Miller compensation technology, so that circuit system stability is ensured, further, system bandwidth is greatly increased, a capacitor is not used, and the area of a chip is greatly reduced.

Description

technical field [0001] The invention relates to an operational amplifier. Background technique [0002] The operational amplifier is one of the most basic unit circuit modules in modern integrated circuits, and the two-pole differential amplifier is superior based on its high power supply noise suppression ability and larger output voltage swing. There are usually many poles in the internal circuit of the two-pole differential op amp, which causes the phase to shift, that is, the amplitude-frequency curve does not drop to 1 before the phase-frequency curve approaches -180°. Therefore, the stability and frequency compensation of the two-pole op amp is of great significance. [0003] With the continuous decline of power supply voltage and the improvement of various performance indicators, the previous frequency compensation structure of operational amplifiers can no longer meet the requirements of circuit design. At the same time, it is necessary to improve the signal-to-nois...

AI Technical Summary

Problems solved by technology

[0005] The disadvantages of the existing frequency compensation technology are: (1) Using Miller capacitance compensation to calculate the distribution of poles and zeros can predict the frequency of the main poles more accurately, but it cannot effectively predict the frequency of the zero point and the sub-pole of the circuit. That is, it is difficult to ensure that the zero poles are completely canceled, especially when the load capacitance is unknown or changes

(2) When it comes to the specific realization of the resistance, the resistance is generally realized by the equivalent resistance of the MOS transistor working in the linear region, but the transistor is not only related to the process, but the prerequisite for using it is to assume that the transistor obeys the square law characteristic, so the scheme There will be a large error, and the system cannot be stabilized accurately

(3) Due to the introduction of capacitors, the chip area and power consumption will be greatly increased. At the same time, because the capacitors push the main pole lower, the unity gain bandwidth product will be reduced.

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