Bidirectional HEMT Substrate Biasing for Lower-Potential Clamping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Bidirectional high electron mobility transistors (HEMTs) face challenges with capacitive coupling between the channel and substrate, which affects reliability and stability, especially when dealing with high voltages and two source terminals.
Innovation Solution
A biasing circuit is introduced that includes a combination of enhancement mode (EMODE) and depletion mode (DMODE) HEMTs, coupled in series and cross-coupled configurations, to bias the substrate at the lower potential of the two source terminals, ensuring reliable operation by clamping the substrate voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple electrical contact is used to tie the substrate to a source terminal in a bidirectional switch, then the device structure remains simple, but the substrate cannot be properly biased when either source terminal assumes high voltage, leading to capacitive coupling issues
Solution Approach 1:
The substrate biasing circuit dynamically adjusts the substrate potential based on the instantaneous voltage levels at the two source terminals. The circuit automatically switches between connecting the substrate to the first source terminal or the second source terminal depending on which terminal is at lower potential, enabling the substrate to adaptively track the lower potential source and eliminate capacitive coupling issues in bidirectional operation
Solution Approach 2:
A dedicated substrate biasing circuit is introduced as an intermediary component between the two source terminals and the substrate. This biasing circuit acts as a mediator that selectively connects the substrate to the appropriate source terminal through controlled switching mechanisms, preventing direct capacitive coupling while maintaining proper substrate potential
2Reliability
If the substrate is tied to a fixed potential in conventional unidirectional devices, then capacitive coupling is eliminated and reliability is improved, but this approach cannot be applied to bidirectional switches with two source terminals at different potentials
Solution Approach 1:
The substrate biasing circuit dynamically adjusts the substrate potential based on the instantaneous voltage levels at the two source terminals. The circuit automatically switches between connecting the substrate to the first source terminal or the second source terminal depending on which terminal is at lower potential, enabling the substrate to adaptively track the lower potential source and eliminate capacitive coupling issues in bidirectional operation
Solution Approach 2:
The substrate biasing circuit is designed to handle multiple operating conditions of bidirectional switches, including both source terminals at different potentials, both terminals switching roles, and various voltage levels. This multi-functional biasing circuit maintains proper substrate potential regardless of which source terminal is at higher or lower potential, making the device universally applicable to bidirectional operation
Data Source
AI summary
Embodiments of the present disclosure provide a semiconductor device, including: a high electron mobility transistor (HEMT) bidirectional switch including: a first source at a first potential; a second source a second potential different than the first potential; and a substrate; and a biasing circuit, coupled to the first source of the bidirectional switch and the second source of the bidirectional switch, for biasing the substrate at a potential equal to the lower of the first potential of the first source of the bidirectional switch and the second potential of the second source of the bidirectional switch.