Constant Voltage Circuit Using Third Transistor to Boost Current
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Solution Overview
Problem
Conventional constant voltage generating circuits with ED-type reference voltage supplies lack sufficient current supplying ability, necessitating the use of a buffer amplifier, which increases circuit complexity.
Innovation Solution
A constant voltage generating circuit design utilizing a depletion-type and enhancement-type NMOSFET in series between a power supply and ground, with a third transistor connected to output the constant voltage, enhancing current supply without requiring a buffer amplifier, thereby reducing circuit scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a buffer amplifier is added to enhance current supplying ability, then current supply capability is improved, but circuit scale increases
Solution Approach 1:
The patent merges the reference voltage generation function with the current supply function by adding a third transistor that shares the constant voltage node. This integration allows the circuit to provide both stable reference voltage and sufficient current to the load without requiring a separate buffer amplifier stage, thereby improving current supplying ability while avoiding the increase in circuit scale that would result from adding a buffer amplifier.
2Power
If a buffer amplifier is used to improve current supply, then current capability is enhanced, but circuit configuration becomes more complex
Solution Approach 1:
The third transistor in the patent serves multiple functions: it provides current amplification to enhance current supply capability, maintains the constant voltage at the output node, and connects the reference voltage supply to the load. This multi-functionality eliminates the need for a dedicated buffer amplifier, thereby enhancing current capability while keeping the circuit configuration simple.
3Device complexity
If ED-type reference voltage supply is used with simple configuration, then circuit simplicity is achieved, but current supplying ability is insufficient
Solution Approach 1:
The third transistor acts as an intermediary element between the ED-type reference voltage supply and the load. It receives the constant voltage from the simple ED-type supply and provides current amplification to drive the load, thereby bridging the gap between the simple reference voltage generation circuit and the requirement for sufficient current supply capability.
Data Source
AI summary
A constant voltage generating circuit includes an ED-type reference voltage supply that generates a predetermined constant voltage by using a first transistor of depletion-type and a second transistor of enhancement-type that are connected in series between a power supply terminal and a ground terminal, and a third transistor a source of which is connected to an output terminal for the constant voltage, a drain of which is connected to the power supply terminal or the ground terminal, and a gate of which is connected to a connection node between the first transistor and the second transistor.