Bootstrapped Switch Circuit for Faster NMOS Gate Drive
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Solution Overview
Problem
Conventional bootstrapped switches have limitations in speed and response time due to the design of the switch controlling the NMOS transistor, which affects their performance in operating faster and generating accurate samplings.
Innovation Solution
The proposed bootstrapped switch includes additional components such as capacitors and resistors to instantaneously boost the voltage at the control terminal of the transistor, enhancing the switching speed by rapidly turning the switch on and off, with the use of logic circuits and transistors to manage clock signals and reference voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional switch design is used to control the NMOS transistor, then the device complexity is lower, but the response time is longer and switching speed is slower
Solution Approach 1:
The control switch is divided into multiple transistor stages (first transistor, second transistor, third transistor) that operate in sequence. Each transistor stage processes the control signal independently, allowing the overall switching action to be broken down into manageable segments that can be optimized for speed without excessive complexity in any single stage.
Solution Approach 2:
Bootstrap capacitors are introduced as intermediary energy storage elements between the control signal source and the NMOS transistor gate. These capacitors act as mediators that can rapidly transfer charge to the gate, enabling fast switching transitions without requiring a complex high-speed switch directly at the gate control point.
2Loss of time
If additional components are added to boost voltage at the control terminal, then the response time is reduced, but the device complexity increases
Solution Approach 1:
The bootstrap capacitors are pre-charged to a specific voltage level during the non-switching period. This preliminary charging action prepares the energy storage elements in advance, so that when switching is required, the pre-charged capacitors can immediately discharge to provide the necessary voltage boost at the control terminal, reducing response time without requiring complex real-time voltage generation circuitry.
Solution Approach 2:
The voltage parameter at the control terminal is dynamically changed through the bootstrap capacitor discharge mechanism. By controlling when and how the bootstrap capacitors discharge, the voltage at the control terminal can be rapidly adjusted to the required level, achieving fast response time while using relatively simple capacitor and switch components rather than complex voltage regulation circuitry.
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
This configuration allows the bootstrapped switch to operate at a higher speed and respond more rapidly compared to prior art, as demonstrated by simulations showing improved voltage transitions and switching performance.
Implementation Method 1
The first transistor receives the input voltage at the first terminal and outputs the output voltage at the second terminal
Implementation Method 2
The first capacitor has a third terminal and a fourth terminal
Implementation Method 3
The resistor is coupled between the third control terminal and the second reference voltage
Data Source
AI summary
A bootstrapped switch includes a first transistor, a second transistor, a first capacitor, three switches, and a switch circuit. The switch circuit includes a first switch, a second switch, a second capacitor, and a resistor. The first transistor receives the input voltage and outputs the output voltage. The first terminal of the second transistor receives the input voltage, and the second terminal of the second transistor is coupled to the first terminal of the first capacitor. The control terminal of the first switch receives a clock. The second switch is coupled between the control terminal of the first transistor and the first switch. The second capacitor is coupled between the control terminal of the first switch and the control terminal of the second switch. The resistor is coupled between the control terminal of the second switch and a reference voltage.