Bootstrapped Switch Circuit for Body-Diode Leakage Blocking
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Solution Overview
Problem
Existing switch circuits face performance degradation due to current leakage caused by body diodes, and existing control mechanisms can alter switch parameters in a destructive manner, necessitating improved control mechanisms that do not degrade switch performance.
Innovation Solution
A four-quadrant bootstrapped switch circuit configuration with coupled sources and gates of transistors, utilizing a floating voltage source and driver to generate constant gate-to-source voltages for controlling the transistors, ensuring the switch is turned on or off based on predetermined voltage thresholds, thereby preventing current leakage and maintaining performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single transistor is used as a switch, then the device complexity is low, but current leakage occurs due to the forward biased body diode
Solution Approach 1:
Two transistors are combined in a back-to-back configuration where the drain of one transistor connects to the drain of the other, and the sources are connected together. This merging creates a single switch unit that blocks current in both directions, eliminating the body diode leakage problem while maintaining a relatively simple overall structure.
Solution Approach 2:
A bootstrapped capacitor is introduced as an intermediary element that stores charge and maintains a constant voltage potential between the connected sources and gates. This intermediary component enables precise voltage control of the transistors, ensuring they remain properly biased and preventing any residual current leakage paths.
2Ease of operation
If control signals are applied to the transistor gate, then the switch can be turned on and off, but the control signal changes switch parameters in a destructive manner
Solution Approach 1:
The bootstrapped capacitor is pre-charged to a specific voltage level before the switch operation begins. This preliminary action establishes a reference potential that ensures the transistor gates are always biased correctly relative to their sources, preventing parameter degradation during switching operations.
Solution Approach 2:
The bootstrapped capacitor dynamically adjusts the voltage potential between the connected sources and gates during operation. By changing this voltage parameter in a controlled manner, the transistors maintain optimal bias conditions throughout the switching cycle, preventing destructive parameter changes while enabling full control functionality.
Data Source
AI summary
A bootstrapped switch circuit includes a first switch transistor to receive an input signal and a second switch transistor to provide an output signal. The sources of the switch transistors may be coupled. A voltage source may be coupled to the sources of the switch transistors and at least one of the gates of the switch transistors. The voltage source may generate a control voltage to activate at least one of the switch transistors based on a bias current. A voltage source driver may be coupled to the voltage source to generate the bias current based on a bias voltage. The bias voltage may include a first voltage approximately corresponding to an overdrive voltage of at least one of the switch transistors and a second voltage approximately corresponding to a threshold voltage of the switch transistors.