Analog Switch Feedback Circuit for Low Harmonic Distortion
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Solution Overview
Problem
Conventional analog switch circuits suffer from significant harmonic distortion, particularly in low load conditions, due to variations in channel resistance caused by input signals and ambient temperature, leading to unsatisfactory performance in reducing harmonic distortion.
Innovation Solution
An adaptive control mechanism is implemented, using a sensor circuit and gate-source voltage adjustment circuit to maintain a constant channel resistance by dynamically adjusting the gate-source voltage based on the voltage difference between the input and output signals, thereby reducing harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional analog switch circuits use fixed gate-source voltage for MOS devices, then the circuit structure is simple, but channel resistance varies with input signal and temperature causing serious harmonic distortion
Solution Approach 1:
The patent implements a feedback control mechanism where the gate-source voltage adjustment circuit continuously monitors the channel resistance (through voltage difference sensing between input and output) and dynamically adjusts the gate-source voltage to maintain constant channel resistance. This closed-loop feedback system eliminates the harmonic distortion caused by resistance variations while keeping the overall circuit structure relatively simple.
Solution Approach 2:
The patent changes the gate-source voltage parameter dynamically based on the operating conditions. By adjusting the gate-source voltage in response to input signal amplitude and temperature variations, the channel resistance is kept constant, thereby reducing harmonic distortion without requiring complex circuit topology.
2Quantity of substance
If the load resistance is reduced to achieve light load condition, then the circuit can handle smaller currents, but the harmonic distortion becomes more serious
Solution Approach 1:
The feedback control mechanism continuously adapts the gate-source voltage based on the actual channel resistance, which varies with load conditions. This ensures that even in light load conditions with reduced load resistance, the channel resistance remains constant, preventing the increase in harmonic distortion that would otherwise occur.
Solution Approach 2:
The patent makes the gate-source voltage dynamic rather than fixed, allowing it to adapt to changing load conditions. This dynamic adjustment ensures optimal performance across the full range of load currents, maintaining low harmonic distortion whether the circuit is operating in heavy load or light load conditions.
3Ease of operation
If PMOS and NMOS devices use constant gate voltage, then the circuit is easy to control, but the gate-source voltage varies with input signal causing channel resistance variation and increased distortion
Solution Approach 1:
The gate-source voltage adjustment circuit provides automatic feedback control that maintains constant channel resistance without requiring complex manual control. The circuit self-regulates by sensing the voltage difference across the switch and adjusting the gate-source voltage accordingly, preserving ease of operation while eliminating channel resistance variation.
Solution Approach 2:
The circuit performs self-adjustment through the feedback mechanism, automatically compensating for variations in gate-source voltage caused by input signal changes. This self-service capability maintains constant channel resistance without external intervention, keeping the control simple while eliminating the harmful resistance variations.
Data Source
AI summary
An analog switch circuit includes: a switch unit and a control circuit, wherein the control circuit includes a sensor circuit and a gate-source voltage adjustment circuit. The switch unit operates a first switch therein according to a first gate-source voltage, to convert an input signal of an input terminal to an output signal of an output terminal. The sensor circuit is coupled between the input terminal and the output terminal, and generates a sensing signal according to a voltage difference between the input signal and the output signal. The gate-source voltage adjustment circuit is coupled to the sensor circuit, and adaptively adjusts the first gate-source voltage according to the sensing signal, to maintain the conduction resistance of the switch unit at a constant while the voltage difference changes.