Charge-Steering Amplifier Feedforward Isolation of Common-Mode Perturbations
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Solution Overview
Problem
Conventional charge-steering differential amplifiers are susceptible to common mode voltage perturbations, which degrade their performance and stability by affecting the gain of the amplifier.
Innovation Solution
A charge-steering amplifier circuit incorporating a sample and hold circuit and a reference voltage generating circuit that isolates and cancels common mode voltage perturbations through a feedforward mechanism, ensuring the gate-source voltages of transistors are not affected by common mode voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional charge-steering differential amplifier is used, then the circuit structure is simple, but the amplifier performance degrades due to common mode voltage perturbations affecting the gain
Solution Approach 1:
The amplifier circuit is segmented into distinct functional blocks: a charge-steering differential amplifier stage, a common mode voltage detection path, and a compensation path. This segmentation allows independent optimization of each function while maintaining overall system performance and stability against common mode perturbations.
Solution Approach 2:
An intermediary compensation signal is introduced through the third capacitor and control circuit. This intermediary element detects common mode voltage variations and generates compensating signals that counteract the perturbations, thereby protecting the main amplification function from degradation.
2Measurement precision
If the gate-source voltages of transistors are directly affected by common mode voltage, then the circuit operation is simple, but the signal-to-noise-plus-distortion ratio deteriorates
Solution Approach 1:
A feedback mechanism is implemented where the common mode voltage is continuously monitored through detection capacitors and control circuits. The detected common mode voltage information is fed back to adjust the gate-source voltages of the transistors, thereby maintaining high signal-to-noise-plus-distortion ratio despite common mode perturbations.
Solution Approach 2:
The circuit performs preliminary anti-action by detecting common mode voltage perturbations before they significantly affect the gate-source voltages. The control circuit proactively adjusts the transistor gate voltages to counteract incoming common mode disturbances, preventing degradation of the signal-to-noise-plus-distortion ratio.
Data Source
AI summary
This disclosure provides a charging-steering amplifier circuit and the control method thereof. The charging-steering amplifier circuit includes a charging-steering differential amplifier and a sample and hold circuit. The charging-steering amplifier circuit operates in a reset phase or in an amplifying phase to amplify a differential input signal. The control method includes steps of: in the reset phase, obtaining a common mode voltage of the differential input signal according to the differential input signal; in the reset phase, providing the common mode voltage to one of the charging-steering differential amplifier and the sample and hold circuit; in the reset phase, sampling the differential input signal by the sample and hold circuit to generate a voltage signal; and in the amplifying phase, inputting the voltage signal to the charging-steering differential amplifier.