Transconductance constant control circuit and rail-to-rail operational amplifier

Abstract

Embodiments of the invention provide a transconductance constant control circuit and a rail-to-rail operational amplifier, and relate to the technical field of integrated circuits. The transconductance constant control circuit comprises a first switch, a second switch, and a control unit. The control unit is electrically connected to the first switch and the second switch. One end of the first switch is electrically connected between a bias circuit and a first input unit, and the other end of the first switch is grounded. One end of the second switch is electrically connected between the biascircuit and a second input unit, and the other end of the second switch is electrically connected to a power supply. The input end of the control unit is electrically connected to the input end of thefirst input unit and the input end of the second input unit. The control unit is used for controlling one of the first switch and the second switch to open or close according to an input signal, so that one of the first input unit and the second input unit works normally, thereby achieving the constant transconductance of the rail-to-rail operational amplifier.

Description

technical field [0001] The invention relates to the technical field of integrated circuits, in particular to a transconductance constant control circuit and a rail-to-rail operational amplifier. Background technique [0002] Transconductance refers to the ratio of the output current of a circuit unit to the input voltage. When an op amp is used as a buffer, a common-mode input range as large as the input signal range is required, requiring a rail-to-rail op amp for large dynamic range. like figure 1 As shown, the common-mode input (Vcm) of the rail-to-rail operational amplifier can be from the ground level (gnda) to the supply voltage (vdda), when the common-mode input of the rail-to-rail operational amplifier changes from the ground level to the supply voltage, The variation range of the transconductance of the rail-to-rail operational amplifier is very large and cannot be kept constant, resulting in difficulty in frequency compensation, large changes in gain and unity ga...

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Problems solved by technology

like figure 1 As shown, the common-mode input (Vcm) of the rail-to-rail operational amplifier can be from the ground level (gnda) to the supply voltage (vdda), when the common-mode input of the rail-to-rail operational amplifier changes from the ground level to the supply voltage, The range of transconductance of the rail-to-rail operational amplifier is very large and cannot be kept constant, resulting in difficulty in frequency compensation, large changes in gain and unity gain bandwidth, and severe instability of circuit performance in high frequency bands

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