GaN Comparator Hysteresis Using a Programmable Depletion-Mode Device
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Solution Overview
Problem
Existing hysteretic comparators in GaN are process-dependent due to variability in GaN Vth, and they lack effective noise protection and programmability.
Innovation Solution
A circuit comprising a comparator, a transistor, and a depletion mode device with a control gate connected to ground, where the transistor's ON and OFF states control the pinch-off voltage of the depletion mode device, providing noise protection and programmability independent of GaN Vt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a multiplier based on GaN HEMT Vth is used to set hysteresis voltage, then the hysteresis comparator can be implemented in GaN technology, but the hysteresis becomes extremely process dependent due to GaN Vth variability
Solution Approach 1:
The patent changes the controlling parameter from GaN Vth (which varies with process) to a bandgap reference voltage (which is stable and process-independent). The hysteresis voltage is now determined by the ratio of resistors and the stable bandgap reference, eliminating process dependency while maintaining GaN implementation compatibility.
Solution Approach 2:
The patent introduces a bandgap reference circuit as an intermediary element that provides a stable reference voltage independent of GaN process variations. This intermediary decouples the hysteresis voltage from direct dependence on GaN Vth, allowing the comparator to maintain stable operation across process variations.
2Ease of operation
If existing hysteretic comparators are used in GaN, then comparison function is provided, but noise protection is insufficient due to lack of hysteresis control
Solution Approach 1:
The patent implements positive feedback through the hysteresis mechanism where the output voltage is fed back to the inverting input through the hysteresis voltage. This feedback creates hysteresis loops that provide noise immunity by requiring a minimum voltage change to trigger state transitions, effectively filtering out noise spikes while maintaining comparison functionality.
3Ease of operation
If existing comparators are used, then basic comparison is achieved, but programmability is lacking due to fixed hysteresis voltage
Solution Approach 1:
The patent makes the hysteresis voltage dynamic and programmable by using resistor dividers that can be configured through control signals. The hysteresis voltage is no longer fixed but can be adjusted by changing the resistor ratios, enabling programmable comparison thresholds and adapting the comparator to different application requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides hysteresis that is independent of GaN Vt and allows for programmability with a ground-referenced programming voltage, effectively protecting against noise spikes and enabling stable operation.
Implementation Method 1
a depletion mode device connected to ground and comprising a control gate connected to the transistor
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.