Voltage Reference Circuit Input Current Compensation
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Solution Overview
Problem
Existing voltage reference circuits assume negligible input current, which is no longer valid for modern MOSFETs with thin gate oxides and BJTs, leading to imbalance and unpredictability in output voltage due to non-negligible input currents.
Innovation Solution
A voltage reference circuit design incorporating three or more current mirrors, an operational amplifier, a voltage buffer, diodes, and resistors to compensate for non-negligible input currents, ensuring balanced transistor operation and minimizing the effects of input current on output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If MOSFETs with thin gate oxides or BJTs are used to reduce device size and improve integration, then device scaling and integration density are improved, but non-negligible input current flows into gate or base terminals causing imbalance and unpredictability in voltage reference output
Solution Approach 1:
The patent converts the harmful effect of non-negligible input current into a beneficial compensation mechanism. Current mirror circuits are designed to intentionally replicate and balance the input current flowing into transistor terminals, transforming what was previously an uncorrected error source into a controlled parameter that maintains circuit balance and voltage reference stability despite using scaled devices with thin gate oxides or BJTs.
Solution Approach 2:
The patent implements feedback through current mirror circuits that continuously monitor and replicate the input current flowing into transistor terminals. This feedback mechanism detects the input current imbalance and automatically adjusts the circuit operation to maintain balance, ensuring stable voltage reference output even when using modern scaled MOSFETs or BJTs with significant input current.
2Reliability
If input current compensation circuits are added to balance current mirrors, then voltage reference stability is improved, but device complexity increases
Solution Approach 1:
The patent achieves multi-functionality by designing current mirror circuits that simultaneously perform their traditional current replication function and the additional function of input current compensation. The same circuit elements that mirror currents between branches also inherently compensate for input current effects by maintaining balance, eliminating the need for separate compensation circuits and reducing overall device complexity.
Data Source
AI summary
A voltage reference circuit includes three or more current mirrors, an operational amplifier, a voltage buffer, two or more diodes, and one or more resistors. The operational amplifier has two inputs separately coupled to an output of two of the three or more current mirrors and an output coupled to the three current mirrors. The voltage buffer has an input coupled to an output of the other one of the three or more current mirrors and another input coupled to an output of the voltage buffer. Each of the diodes is coupled between the output of the two of the three or more current mirrors and one of ground and a negative supply. The one or more resistors are coupled to an output of one or more of the three or more current mirrors to tune effects of input current and establish a first set absolute voltage and temperature coefficient on a voltage reference.