Bootstrap Gate Drive Circuit for Threshold-Independent Output
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Solution Overview
Problem
Conventional bootstrap circuits in semiconductor devices face issues with variations in threshold voltages of transistors, leading to fluctuations in output potentials, which can result in either high voltage stress or insufficient conduction, affecting the reliability and performance of the circuit.
Innovation Solution
A bootstrap circuit design that controls the supply of potentials to the gate electrode of the output transistor using multiple power sources and circuits, allowing independent determination of the voltage changes due to the bootstrap effect, thereby reducing the impact of manufacturing variations in transistors and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-conductivity-type MOS transistor circuit is used, then manufacturing cost is reduced, but power consumption increases and output margin decreases
Solution Approach 1:
The bootstrap circuit pre-charges the gate electrode of the output transistor to a high potential before the output transistor needs to conduct. This preliminary action ensures that when the output transistor turns on, the gate already has sufficient potential to overcome threshold voltage variations, maintaining reliable conduction with a single-conductivity-type transistor circuit.
Solution Approach 2:
The invention introduces a bootstrap circuit as an intermediary mechanism between the power source and the output transistor gate. This intermediary circuit uses a capacitor to transfer and store potential, mediating the voltage delivery to ensure stable operation despite transistor parameter variations, thereby resolving the contradiction between using simple single-type transistors and maintaining reliable performance.
2Ease of manufacture
If conventional bootstrap circuit is used, then single-conductivity-type transistors can be used, but variations in transistor threshold voltages cause fluctuations in output potentials
Solution Approach 1:
The gate electrode is pre-charged to a high potential through the bootstrap capacitor before the output transistor needs to operate. This preliminary charging action ensures that regardless of threshold voltage variations, the gate always starts with sufficient potential to maintain stable output, eliminating the reliability issue while keeping the simple single-conductivity-type transistor structure.
3Ease of manufacture
If bootstrap effect is used to output low potential, then single-conductivity-type PMOS circuit can be used, but high voltage stress may occur on transistors
Solution Approach 1:
The bootstrap capacitor pre-charges the gate electrode to a high potential before the output transistor conducts. This preliminary action ensures that the voltage difference across the transistor is minimized during conduction, reducing voltage stress and preventing breakdown while maintaining the simple single-conductivity-type PMOS circuit structure.
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 effectively minimizes the range of voltage variations caused by the bootstrap effect, ensuring high reliability and reduced manufacturing costs by using existing power sources, thus improving the overall performance and stability of semiconductor devices.
Implementation Method 1
a coupling capacitor (25) connected between the source electrode and the gate electrode of the transistor (1)
Data Source
AI summary
A bootstrap circuit includes an output transistor, a bootstrap capacitor provided between the gate and source of the output transistor, a power source, and a circuit that performs ON/OFF control of a supply from the power source to the gate electrode of the transistor. An initial voltage before a bootstrap effect can be set to the potential of the power source, which is independent of the threshold voltage of the transistor. Therefore, the source output of the transistor rising or dropping due to the bootstrap effect is not affected by variations that depend on the threshold voltage of the transistor.