Comparator Hysteresis Circuit Using Depletion-Mode Pinch-Off Control
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Solution Overview
Problem
Existing hysteretic comparators in GaN are process-dependent due to varying GaN threshold voltage, and they lack effective noise protection mechanisms.
Innovation Solution
A circuit comprising a comparator, a transistor, and a depletion mode device with a control gate, where the transistor's output controls the pinch-off voltage of the depletion mode device, providing hysteresis independent of GaN threshold voltage and noise protection using fixed pinch-off depletion mode devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multiplier based on GaN HEMT Vth is used for setting hysteresis voltage, then the hysteresis can be controlled, but the hysteresis becomes extremely process dependent due to GaN Vth variation
Solution Approach 1:
The patent changes the controlling parameter from GaN HEMT threshold voltage (Vth) to a bandgap reference voltage. The bandgap reference provides a stable, temperature-compensated voltage reference that is not affected by process variations in GaN device parameters. This allows hysteresis to be set by resistor ratios rather than device parameters, eliminating process dependence while maintaining controllable hysteresis.
Solution Approach 2:
The patent introduces a bandgap reference circuit as an intermediary between the power supply and the hysteresis control mechanism. This bandgap reference acts as a stable intermediate voltage source that mediates the hysteresis voltage setting, isolating the control mechanism from process variations in the GaN devices while providing a stable reference for precise hysteresis control.
2Reliability
If existing hysteretic comparators are used in GaN, then comparison function is provided, but noise protection mechanism is insufficient
Solution Approach 1:
The patent applies preliminary anti-action by using the hysteresis mechanism to preemptively counteract noise spikes before they can cause false triggering. The hysteresis creates a dead zone around the threshold voltage where small noise variations cannot trigger a state change, thus preliminarily protecting the comparator from noise-induced errors before they occur.
Solution Approach 2:
The patent implements positive feedback through the hysteresis mechanism, where the output voltage is fed back to the non-inverting input through a feedback network. This feedback creates two distinct threshold voltages (upper and lower thresholds) that provide noise immunity. When noise causes the input to fluctuate near the threshold, the feedback maintains the current state until the input exceeds the appropriate threshold, effectively filtering out noise spikes.
Data Source
AI summary
The present disclosure relates to a circuit and, more particularly, to comparator circuits used with a depletion mode device and methods of operation. The circuit includes: a comparator; a transistor connected to an output of the comparator; and a depletion mode device connected to ground and comprising a control gate connected to the transistor.