A current-voltage conversion circuit for sensors

Abstract

A current-to-voltage conversion circuit for sensors includes an output end VOUT and an input end IIN of the current-to-voltage conversion circuit. A cascode input stage and a source follower are connected between the output end VOUT and the input end IIN. The cascode input stage is equipped with a bias circuit which is an auxiliary voltage amplifier. A current source is injected into the drain ofa common-source transistor in the cascode input stage. Because of the high gain of the cascode input stage, the noise of the source follower can be neglected, and the noise of the amplifier is mainlydetermined by the noise of the first cascode input stage. Because of the design of feedback trans-impedance, the circuit can achieve high bandwidth, the circuit can use a larger resistor under the same bandwidth, and noise can be reduced. The design of the auxiliary voltage amplifier increases the equivalent trans-conductance of a common-gate transistor in the cascode stage and reduces the Millereffect of the input stage. The design of the injection current source increases the trans-conductance of the common-source transistor in the cascode stage and reduces the noise at the input end.

Description

technical field [0001] The invention belongs to the technical field of current-voltage conversion circuits, and relates to a current-voltage conversion circuit for sensors; in particular, it relates to a current-voltage conversion application circuit for gas parameter detection sensors. Background technique [0002] The current-voltage conversion circuit in commonly used sensor systems is often implemented by a common-gate amplifier circuit, which has the advantage of small input impedance and can increase the amplifier rate. Such as figure 1 Shown is a common-gate preamplifier implemented with MOSFETs. Neglecting the influence of secondary non-ideal effects such as channel length modulation and body effect, the equivalent input impedance is on the order of 1 / gm, and gm is the equivalent transconductance of the input tube. Selecting a suitable bias current source can easily achieve input bandwidth of maximization. However, this comes at the expense of output voltage swing...

AI Technical Summary

Problems solved by technology

However, this comes at the expense of output voltage swing, making the dynamic range performance of the amplifier limited

[0003] Common gas parameter detection sensors have a small output current, so the noise performance requirements of the sensor application circuit are relatively high

Therefore, when the current-voltage conversion circuit in the sensor detection system uses a common-gate amplifier circuit, the noise performance is poor, and it cannot meet the low-noise performance requirements of the high-performance current-voltage conversion circuit.

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