Bandgap Reference Circuit With Offset-Canceling Voltage Sampling
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Solution Overview
Problem
Existing reference voltage circuits using operational amplifiers suffer from significant errors in bandgap voltage due to offset voltage effects.
Innovation Solution
A reference voltage circuit is designed with a voltage output circuit that amplifies voltages at specific nodes for alternating time periods, and a first amplifier circuit that reduces the impact of offset voltages by amplifying the difference between voltages stored in capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an operational amplifier is used to generate bandgap voltage, then the reference voltage circuit can be implemented with a simple structure, but the error in bandgap voltage becomes large due to offset voltage effects
Solution Approach 1:
The patent divides the voltage amplification process into two separate time periods: a first time period for amplifying a first voltage at a first node, and a second time period for amplifying a second voltage at a second node. This temporal segmentation allows each amplification operation to be performed independently, reducing the impact of offset voltage errors that would affect simultaneous amplification of multiple signals.
Solution Approach 2:
The voltage output circuit operates repeatedly with a predetermined frequency, alternating between the first time period and the second time period. This periodic operation enables the circuit to sequentially amplify different voltages and store them in separate capacitors, then allows the amplifier circuit to compute the difference between these stored voltages, thereby eliminating offset voltage effects through differential measurement.
2Measurement precision
If offset voltage effects are reduced through circuit design, then bandgap voltage accuracy is improved, but the circuit configuration becomes more complex
Solution Approach 1:
The patent merges the amplification of multiple voltages into a single amplifier circuit by sequentially processing different voltages at different time periods. Instead of using separate amplifiers for each voltage signal, the circuit uses one amplifier circuit that alternates between amplifying the first voltage and the second voltage, then computes their difference. This merging approach reduces the number of amplifier components while maintaining accuracy.
Solution Approach 2:
The voltage output circuit performs multiple functions using a single operational structure. It sequentially amplifies different voltages, stores them in capacitors, and enables the amplifier circuit to compute differences between stored voltages. This multi-functional design reduces the overall component count while achieving the goal of offset voltage rejection.
Data Source
AI summary
A reference voltage circuit includes: a first resistor and a first pn junction device connected in series, and a second resistor, a third resistor, and a second pn junction device connected in series, both between a predetermined line and a ground; a first capacitor and a second capacitor; a voltage output circuit configured to amplify a first voltage at a first node between the first resistor and the first pn junction device, and amplify a second voltage at a second node between the second resistor and the third resistor, for a first time period and a second time period to thereby output a resultant voltage to the first capacitor and the second capacitor, respectively; and an amplifier circuit configured to amplify a difference between voltages at the first and second capacitors. A reference voltage corresponding to a voltage from the first amplifier circuit is applied to the predetermined line.