Cascode Sensor Circuit With Feedback for Low-Power Linear Readout
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Solution Overview
Problem
Existing sensor circuits for measuring physical quantities face challenges in reducing power consumption and area while maintaining high performance, particularly in MEMS-based devices, due to the need for constant biasing current and noise issues associated with biasing circuits.
Innovation Solution
A sensor circuit utilizing a telescopic or folded cascode configuration with field-effect transistors, where the biasing circuit serves as the amplification circuit, allowing current re-use and reducing noise, and incorporating a feedback arrangement to provide a highly linear readout with reduced power consumption and area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant biasing current is used for signal recovery in resistive sensors, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent merges the biasing function and amplification function into a single circuit block. The amplifier is configured to simultaneously provide bias current to the resistive sensor and amplify the sensor output signal, eliminating the need for separate biasing current sources and reducing overall power consumption while maintaining measurement precision
2Measurement precision
If separate biasing and amplification circuits are used, then measurement precision is improved, but device area increases
Solution Approach 1:
The patent combines the biasing circuit and amplification circuit into a single integrated amplifier block. This merger reduces the total device area while maintaining the functional separation needed for precise signal recovery, as the same amplifier circuit performs both biasing and signal amplification functions
3Measurement precision
If high supply voltage is used for Wheatstone bridge configuration, then dynamic range is improved, but power consumption increases
Solution Approach 1:
The patent employs feedback mechanisms within the amplifier circuit to maintain high dynamic range measurements without requiring high supply voltages. The feedback allows the circuit to operate efficiently at lower voltages while preserving the ability to measure large signal variations, thus reducing power consumption without sacrificing dynamic range
Data Source
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AI summary
Proposed is a sensor circuit for measuring a physical quantity, wherein the sensor circuit comprises at least one sensing composition comprising a variable resistor having a resistance depending on the physical quantity; a first amplifier arrangement for outputting an output signal based on the resistance of the variable resistor, wherein the first amplifier arrangement comprises one field-effect transistor or a plurality of field-effect transistors in a telescopic cascode configuration or a plurality of field-effect transistors in a folded cascode configuration, wherein the first amplifier arrangement comprises an outer source terminal and an outer drain terminal, wherein a first terminal of the variable resistor is connected to the outer source terminal, such that the field-effect transistor having the outer source terminal and the variable resistor form a series circuit; a feedback arrangement for feedbacking at least a part of the output signal of the first amplifier arrangement, which is obtained at the outer drain terminal, to at least one gate terminal of the field-effect transistors of the amplifier arrangement, wherein the feedback arrangement comprises at least one passive or active electronic component, which connects the outer drain terminal to the gate terminal of the field-effect transistor having the outer source terminal; and a first current source for biasing the series circuit of the field-effect transistor having the outer source terminal and the variable resistor.