GaN HEMT Circuit Voltage Clamping for Withstand
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Solution Overview
Problem
GaN-HEMTs have insufficient withstand voltage for high voltage operations due to the breakdown of the thin insulating layer under the gate when electrostatic noise reaches several hundred volts, despite enhancements from field plates increasing source-drain withstand voltage.
Innovation Solution
A transistor circuit design incorporating a first high electron mobility transistor with a field plate and a second high electron mobility transistor with a negative threshold voltage, where the second transistor's source is coupled to the first transistor's gate, and its gate is coupled to the first transistor's source, to limit the source-gate voltage and prevent breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a thin insulating layer is provided directly underneath the gate to enable low-voltage operation, then the transistor can be driven by several volts, but the withstand voltage becomes insufficient and the insulating layer breaks down under high voltage or electrostatic noise
Solution Approach 1:
A second HEMT is introduced as an intermediary protective device between the noise source and the first HEMT's gate. This second transistor limits the voltage applied to the first HEMT's gate through its threshold voltage characteristics, preventing breakdown while allowing normal operation. The second HEMT acts as a voltage-clamping mediator that reconciles the conflict between low operating voltage and high withstand voltage requirements.
Solution Approach 2:
The second HEMT is configured to preemptively limit excessive voltage before it can damage the first HEMT's gate insulating layer. By coupling the second HEMT's source to the first HEMT's gate and its gate to the first HEMT's source, the circuit creates preliminary protection that activates when voltage exceeds the second HEMT's threshold, preventing the harmful high voltage from reaching the vulnerable thin insulating layer.
Data Source
AI summary
A transistor circuit includes a first high electron mobility transistor and a second high electron mobility transistor having a negative threshold voltage, wherein a source of the second high electron mobility transistor is coupled to a gate of the first high electron mobility transistor, and a gate of the second high electron mobility transistor is coupled to a source of the first high electron mobility transistor.