Voltage Regulator Gate-Source Voltage Control for BTI Offset Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional voltage regulators experience offset in output voltage due to bias temperature instability (BTI) affecting PMOS transistors differently when the output terminal voltage drops, leading to imbalance in threshold voltages and differential amplification errors.
Innovation Solution
A voltage regulator with a differential amplifier circuit and voltage control circuits that manage the gate-source voltage of PMOS transistors, using GS and GG voltage limiting circuits to clamp voltages at the tail connection points and gates, ensuring equal or lower voltage differences to mitigate the effects of short-circuits and prevent offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output terminal voltage drops due to a short-circuit, then the gate voltage of the first input transistor drops to ground level, but this causes bias temperature instability to affect the first and second input transistors differently, resulting in threshold voltage offset
Solution Approach 1:
A diode is introduced as an intermediary component connected between the gate of the first input transistor and the tail connection point. This diode acts as a mediator that allows the gate voltage to drop to a controlled level (one diode forward voltage above the tail connection point) during short-circuit conditions, rather than dropping directly to ground. This intermediary protection mechanism prevents gate breakdown while maintaining more balanced operating conditions for both input transistors, thereby reducing threshold voltage offset caused by BTI.
2Reliability
If a diode is connected between the gate and source of the first input transistor to prevent gate breakdown, then the gate voltage is clamped during overshoot, but this configuration causes significant voltage difference between the first and second input transistors during ground short-circuit, exacerbating BTI effects
Solution Approach 1:
The diode is repositioned to connect between the gate of the first input transistor and the tail connection point rather than between gate and source. This intermediary placement ensures that during ground short-circuit conditions, both input transistors experience similar voltage differences relative to their source terminals, maintaining more balanced operating conditions and reducing differential amplification errors caused by asymmetric BTI effects.
Solution Approach 2:
By connecting the diode to the tail connection point (which is at a fixed potential determined by the current source), the gate voltage of the first input transistor is clamped to maintain a constant voltage difference relative to its source, similar to the second input transistor. This creates equipotential conditions for both input transistors during short-circuit events, minimizing threshold voltage offset and maintaining differential amplification accuracy.
Data Source
AI summary
A voltage regulator which includes a differential amplifier circuit containing a first and second input transistors, controlling a gate-source voltage in each of the first and second input transistors including: a current source configured to drive the differential amplifier circuit; the first input transistor containing a gate; the second input transistor containing a gate; and a voltage controller including at least one of a first voltage control circuit to control a voltage at a tail connection point, a second voltage control circuit to control the voltage at the gate of the first input transistor, a third voltage control circuit to control the voltage at the tail connection point, and a fourth voltage control circuit to control the voltage at the gate of the second input transistor.