Analog Sample Circuit With Constant-VGS PMOS Switches
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Solution Overview
Problem
Conventional analog sample circuits face issues with sampling signals below the minimum operating voltage, leading to improper operation of PMOSFET and NMOSFET switch circuits due to varying gate-source voltages, resulting in signal distortion and inability to achieve high linearity.
Innovation Solution
The introduction of a constant voltage module and switch control modules in the analog sample circuit stabilizes the gate-source voltage of PMOSFET switches, ensuring a constant on-resistance and enabling proper sampling of low-voltage signals by generating a constant turn-on voltage for PMOSFET switches, independent of the input signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional PMOSFET switch circuit is used for sampling, then the circuit can operate with simple structure, but the gate-source voltage varies with input signal causing varying on-resistance and signal distortion
Solution Approach 1:
The patent changes the gate voltage parameter from a fixed conventional value to a dynamically adjusted value that compensates for input signal variations. The gate voltage is adjusted according to the input signal level to maintain a substantially constant gate-source voltage across the PMOSFET switch, thereby maintaining constant on-resistance and achieving high-linearity sampling without increasing circuit complexity
2Quantity of substance
If the common mode voltage is set to half of maximum operating voltage for maximum signal amplitude, then signal amplitude is maximized, but signals below minimum operating voltage cannot be sampled properly
Solution Approach 1:
The patent makes the gate voltage dynamic rather than fixed. The gate voltage is adjusted in real-time based on the input signal level, allowing the switch circuit to adapt to different input voltage ranges including signals below the minimum operating voltage. This dynamic adjustment maintains proper switching operation across a wider voltage range while preserving maximum signal amplitude capability
3Reliability
If the gate-source voltage is allowed to vary with input signal for proper switching, then switching operation is maintained, but on-resistance varies causing signal distortion
Solution Approach 1:
The patent compensates for input signal variations by adjusting the gate voltage parameter. When the input signal level changes, the gate voltage is adjusted accordingly to maintain a substantially constant gate-source voltage across the PMOSFET switch. This ensures both reliable switching operation and constant on-resistance, eliminating signal distortion while maintaining proper switching function
Data Source
AI summary
Techniques pertaining to an analog sample circuit are disclosed. One embodiment of the analog sample circuit shows characteristics of low distortion and high linearity, which can be used in many circuits including integrated circuits (IC). In a switch circuit or an analog sample circuit of one embodiment, a constant voltage module is configured to stabilize the gate-source voltage of the PMOSFET switch as the sample switch, so that the gate-resource voltage of the PMOSFET switch doesn't vary with the input signal Vin; a switch circuit is configured to ensure that the switch circuit or the analog sample circuit is capable of processing the input signal lower than a minimum voltage in the circuit.