Multi-Channel Multiplexer Biasing for Low-Leakage Sensor Signals
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Solution Overview
Problem
In multiplexer systems, leakage current through disabled channels can distort sensor signals due to high output impedance of sensors, as even small leakage currents can generate significant voltage across disabled channels, altering the intended signal processed by the system.
Innovation Solution
Incorporating multiple metal oxide semiconductor field effect transistors (MOS transistors) with a bulk biasing circuit and a buffer that couples the internal node of disabled channels to the output voltage level, reducing the drain-to-source potential difference to approximately 0 V and minimizing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sensors are coupled to the multiplexer through multiple channels, then the processing system can selectively process signals from different sensors, but leakage current through disabled channels distorts sensor signals due to high output impedance
Solution Approach 1:
A bulk biasing circuit is introduced as an intermediary between the disabled channel and ground, providing a controlled path for leakage current that prevents it from distorting the sensor signal. The bulk biasing circuit mediates the harmful leakage current by redirecting it through a controlled impedance path, thereby protecting the high-impedance sensor signal from distortion.
Solution Approach 2:
The patent changes the bias voltage parameter applied to the bulk of the transistor in disabled channels. By dynamically adjusting the bulk bias voltage based on the state of the channel (enabled or disabled), the system optimizes the transistor's off-state leakage characteristics. This parameter change reduces leakage current in disabled channels while maintaining proper signal transmission in enabled channels.
2Ease of operation
If transistors are used to enable and disable channels in the multiplexer, then channel selection is achieved, but leakage current flows through transistors when they are off, generating unwanted voltage
Solution Approach 1:
The bulk biasing circuit serves as an intermediary that connects the bulk of the transistor to a controlled voltage source rather than directly to ground or supply. This intermediary circuit provides a controlled impedance path that manages the leakage current flow, preventing the transistor's off-state leakage from generating unwanted voltage that would distort the sensor signal.
Solution Approach 2:
The patent modifies the bulk bias voltage parameter of the transistor to optimize its leakage characteristics. By changing the bulk bias voltage to an intermediate level rather than full supply or ground, the transistor's off-state leakage current is reduced, thereby minimizing the unwanted voltage generated across the high-impedance sensor connection.
3Loss of energy
If small leakage currents flow through disabled channels, then the multiplexer maintains low power consumption, but these small currents generate significant voltage across high output impedance sensors
Solution Approach 1:
The bulk biasing circuit acts as an intermediary that provides a controlled path for the small leakage current, preventing it from flowing through the high-impedance sensor connection. By mediating the leakage current path, the circuit maintains the low power consumption benefit while protecting the sensor signal accuracy from distortion.
Solution Approach 2:
The patent changes the bulk bias voltage parameter to optimize the transistor's leakage characteristics, reducing the magnitude of leakage current to levels that do not generate significant voltage across the sensor's output impedance. This parameter adjustment maintains low power consumption while preserving measurement precision.
Data Source
AI summary
A circuit includes a first switch assembly having a first input node and a first output node, and a second switch assembly having a second input node and a second output node. The circuit further includes a third switch assembly an operational amplifier, and a buffer. The third switch assembly has a third input node and a third output node. The third input node is coupled to the second output node, and the third output node is coupled to the first output node. The buffer has a buffer input and a buffer output. The buffer input is coupled to an input stage of the operational amplifier. The buffer output is coupled to the third switch assembly.