Gate Boosting Transmission Gate With Very-Low-Threshold P-Channel Transistors
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Solution Overview
Problem
The existing integrated circuit technology faces challenges in overdriving p-channel transistors in transmission gates due to the difficulty in providing a negative bias, which complicates the design and limits the scalability of field-programmable gate arrays (FPGAs) as it requires additional circuitry and negative power supply.
Innovation Solution
Fabricating p-channel transistors as very-low-threshold devices allows for easier overdriving by biasing the gate above VDD in the off state, providing additional drive without increasing leakage, thus enabling overdrive on both n-channel and p-channel transistors without additional circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If p-channel transistors are overdriven by providing negative bias voltage, then transmission gate speed is improved, but device complexity and power supply requirements worsen
Solution Approach 1:
The patent changes the threshold voltage parameter of the p-channel transistor by using a very-low-threshold device instead of a standard-threshold device. This allows the transistor to be effectively overdriven with a positive voltage (VDD+0.2V) rather than requiring negative bias voltage, thus improving transmission gate speed without complicating the power supply architecture
Solution Approach 2:
Instead of applying negative voltage to overdrive the p-channel transistor gate (the conventional approach), the patent inverts the approach by using a very-low-threshold device that can be effectively overdriven with positive voltage. This inversion eliminates the need for negative power supply while achieving the same overdrive effect
2Loss of energy
If standard-threshold p-channel transistors are used, then leakage is reduced, but overdrive capability worsens
Solution Approach 1:
The patent changes the threshold voltage parameter from standard to very-low-threshold for the p-channel transistor. This parameter change enables effective overdrive with positive voltage while the transistor design maintains acceptable leakage characteristics through proper sizing and threshold selection
3Speed
If n-channel transistors are overdriven with positive voltage, then transmission gate speed is improved, but area consumption worsens
Solution Approach 1:
The patent changes the threshold voltage parameter of the p-channel transistor to very-low-threshold, which enables effective overdrive with positive voltage. This symmetric overdrive approach for both n-channel and p-channel transistors optimizes the area-speed tradeoff by allowing smaller transistor sizes to achieve the same speed performance
Data Source
AI summary
A gate-boosting transmission gate includes an input node and an output node. An n-channel transistor has a first source/drain terminal connected to the input node and a second source/drain terminal connected to the output node, the n-channel transistor having a low threshold. A p-channel transistor has a first source/drain terminal connected to the input node and a second source/drain terminal connected to the output node, the p-channel transistor having a very low threshold.