MOS Voltage Follower Circuit for Low-Impedance Loads
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Solution Overview
Problem
Conventional voltage follower circuits have a large circuit scale and a high number of elements, which can be inefficient for certain applications.
Innovation Solution
A voltage follower circuit is designed using a first and second MOS transistor, constant current sources, and a depletion type third MOS transistor, reducing the circuit scale and number of elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional voltage follower circuit is composed of an operational amplifier and an output buffer, then the circuit can drive low impedance loads, but the circuit scale becomes large and the number of elements increases
Solution Approach 1:
The patent merges the voltage follower function and buffer driving capability into a single integrated circuit structure using three MOS transistors. The first MOS transistor (Q1) provides the voltage follower function, the second MOS transistor (Q2) provides the buffer driving capability, and the depletion type third MOS transistor (Q3) compensates for voltage drops, combining multiple functions into one compact circuit that eliminates the need for separate operational amplifiers and output buffers
Solution Approach 2:
The patent changes the operating parameters and characteristics of the MOS transistors to achieve both voltage following and buffer functions. By selecting appropriate transistor types (enhancement type vs. depletion type) and configuring their connections, the circuit achieves high input impedance and low output impedance characteristics without requiring traditional operational amplifier structures
Data Source
AI summary
A voltage follower circuit includes a first MOS transistor which has a source connected to an input port, a second MOS transistor which has a source connected to an output port and has a gate and a drain connected to a gate of the first MOS transistor, a first constant current source connected between a drain of the first MOS transistor and a second power supply terminal, a second constant current source connected between the drain of the second MOS transistor and the second power supply terminal, and a depletion type third MOS transistor which has a gate connected to the drain of the first MOS transistor, has a drain connected to a first power supply terminal, and has a source connected to the output port.