Switched Capacitor Amplifier With Impedance Conversion for Fast Gain
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Solution Overview
Problem
Switched capacitor amplifier circuits face challenges in achieving high-speed switching operations and desired voltage gain due to offset voltage cancellation, especially when dealing with high-impedance signal sources, which require larger capacitors and reduce switching speed, and smaller capacitors are prone to discharge due to off-leak currents.
Innovation Solution
Incorporating an impedance converter circuit between the signal source and the first capacitor to convert the output impedance into a specified impedance, allowing for faster charging and discharging of the capacitor while maintaining desired voltage gain, and utilizing a switched capacitor amplifier circuit with specific switching operations to cancel offset voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the value of capacitor C1 is increased to achieve higher voltage gain, then the voltage gain is improved, but the switching speed is reduced
Solution Approach 1:
An impedance converter circuit is introduced as an intermediary between the signal source and the switched capacitor amplifier. This converter transforms the high output impedance of the signal source into a low impedance, enabling the capacitor to charge and discharge rapidly without requiring large capacitance values, thus achieving both high voltage gain and high switching speed
2Quantity of substance
If the value of capacitor C2 is reduced to maintain voltage gain with smaller capacitors, then the capacitor size is reduced, but the electric charge is discharged due to off-leak current
Solution Approach 1:
The impedance converter circuit acts as a mediator that isolates the capacitor from the effects of off-leak current by providing a low-impedance drive. This allows the use of smaller capacitor values while maintaining charge retention, as the converter actively maintains the voltage across the capacitor despite leakage currents
3Productivity
If the switching operation is performed at high speed, then the productivity is improved, but the charging and discharging of capacitor C1 becomes difficult with high-impedance signal sources
Solution Approach 1:
The impedance converter circuit serves as a mediator between the high-impedance signal source and the capacitor, transforming the source impedance to enable rapid charging and discharging operations. This allows high-speed switching to be performed without difficulty, improving productivity while maintaining ease of operation
Data Source
AI summary
A switched capacitor amplifier circuit includes an operational amplifier, a first capacitor and a second capacitor each having one end connected to a negative input terminal of the operational amplifier, a first switching circuit configured to connect the other end of the first capacitor and a signal source during a first operation, a second switching circuit configured to connect the other end of the second capacitor and the output terminal of the operational amplifier so as to connect the output terminal and the negative input terminal of the operational amplifier through the second capacitor during the second operation, and an impedance converter circuit configured to convert an output impedance of the signal source into a specified impedance, the impedance converter circuit being connected between the first switching circuit and the other end of the first capacitor.