Switched Capacitor Amplifier With Impedance Conversion for Fast Gain
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Solution Overview
Problem
Existing switched capacitor amplifier circuits face challenges in achieving high-speed switching operations and desired voltage gain due to high impedance signal sources and off-leak currents, which affect the cancellation of offset voltages.
Innovation Solution
Incorporating an impedance converter circuit between the signal source and the first capacitor, along with a switching circuit configuration that alternates the connection of capacitors to either the signal source or a ground potential, allowing for high-speed charging and discharging of the capacitor while maintaining desired voltage gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the value of capacitor C1 is increased to obtain 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 capacitor C1. This converter transforms the high-impedance signal source into a low-impedance output, enabling fast charging/discharging of capacitor C1 without requiring an excessively large capacitance value, thus resolving the contradiction between voltage gain and switching speed
Solution Approach 2:
The invention changes the impedance parameter of the signal source through the impedance converter circuit. By converting high impedance to low impedance, the circuit enables capacitor C1 to be charged and discharged rapidly, allowing for smaller capacitance values that maintain both high voltage gain and high switching speed
2Speed
If the value of capacitor C2 is reduced to reduce capacitor C1 value, then the switching speed is improved, but off-leak current discharge increases
Solution Approach 1:
The impedance converter circuit acts as a mediator that isolates the effects of capacitor size reductions. By providing a low-impedance drive capability, it allows capacitor C2 to be small for fast switching while the converter ensures that off-leak currents do not significantly discharge the capacitors, maintaining charge retention reliability
3Device complexity
If the signal source has high impedance, then the circuit complexity is reduced, but the switching operation speed is reduced
Solution Approach 1:
The impedance converter circuit serves as a compact intermediary stage that adds minimal complexity while dramatically improving switching speed. It transforms the high-impedance signal source into a low-impedance output capable of rapidly charging and discharging the capacitors, achieving high-speed switching with only one additional operational amplifier and associated components
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.