Operational amplifier for pipeline analog to digital converter

Abstract

The invention discloses an operational amplifier for a pipeline analog to digital converter. The operational amplifier comprises a first main operational amplifier and a second main operational amplifier; the first main operational amplifier comprises a first common source common gate P type transistor pair, a second common source common gate P type transistor pair, a first common source common gate N type transistor pair and a first common source N type transistor pair, which are connected in sequence, and the source electrode of the first common source N type transistor pair is connected with a first tail current N type transistor; the second main operational amplifier comprises a third common source common gate P type transistor pair and a second common source N type transistor pair, which are connected in sequence, and the source electrode of the second common source N type transistor pair is connected with a second tail current N type transistor, wherein the drain electrode of thefirst common source common gate P type transistor pair is connected with the drain electrode of the third common source common gate P type transistor pair through a compensation capacitor. Compared with the prior art, the operational amplifier can greatly improve the gain and the precision of the operational amplifier in the case of low voltage.

Description

technical field [0001] The invention belongs to the field of operational amplifiers, and in particular relates to an operational amplifier for a pipeline analog-to-digital converter. Background technique [0002] With the development of CMOS technology, the characteristic size of MOS transistors has been continuously reduced, and the characteristic frequency has continued to increase, which has also led to the continuous decline of the intrinsic gain of the MOS transistor, and the continuous decline of the power supply voltage, which also makes the design of high-gain operational amplifiers particularly difficult. . The operational amplifier in the first-stage MDAC is extremely demanding in the pipeline analog-to-digital converter, which makes the design of a high-precision high-speed pipeline ADC particularly difficult. [0003] Traditional pipeline operational amplifiers and various levels of residual operational amplifiers are usually implemented with closed-loop high-pe...

AI Technical Summary

Problems solved by technology

This structure increases the output impedance and increases the open-loop gain by adding an auxiliary op amp. However, the added auxiliary op amp will introduce new parasitic capacitance, thereby increasing the pole and reducing the bandwidth of the entire op amp.

The bandwidth of the comparator, the noise on the sampling capacitor, and the load capacitance of each stage all affect the accuracy of the pipeline

Additionally, conventional pipelined op amps cannot achieve high gain at low supply voltages

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