Bandgap Circuit Supply Voltage Compensation
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Solution Overview
Problem
Electronic devices that rely on band gap voltages for calibration and measurement functions are compromised by supply voltage variations, leading to performance and reliability issues due to the dependence of band gap voltage on supply voltage levels.
Innovation Solution
A band gap circuit is designed with a current mirror to match Norton equivalent resistance, using a cascoded output stage and compensation impedance to isolate the band gap voltage from supply voltage variations, ensuring that the band gap voltage remains constant despite changes in supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional band gap circuit is used, then the circuit can provide reference voltage for electronic devices, but the band gap voltage varies significantly with supply voltage changes
Solution Approach 1:
The patent introduces a compensation circuit as an intermediary element that senses supply voltage variations and generates compensating signals to counteract the effects of supply voltage changes on the band gap voltage, thereby isolating the reference voltage from supply variations
Solution Approach 2:
The patent implements a feedback mechanism where the compensation circuit continuously monitors supply voltage changes and adjusts compensation currents or voltages in real-time to maintain constant band gap voltage despite supply variations
2Reliability
If supply voltage independence is improved through compensation circuits, then band gap voltage stability increases, but circuit complexity increases
Solution Approach 1:
The patent combines the compensation function with the existing band gap circuit structure by integrating compensation transistors and impedance elements into the conventional topology, allowing dual functionality without completely redesigning the circuit architecture
Solution Approach 2:
The compensation circuit elements are designed to perform multiple functions: they provide supply voltage compensation while also maintaining proper biasing and operating points for the band gap transistors, reducing the need for separate dedicated compensation components
Data Source
AI summary
This application discusses apparatus and methods for reducing supply voltage induced band gap voltage variation. In an example, a method of compensating a reference voltage current source for supply voltage variation can include providing at least a portion if a reference current for establishing the reference voltage using a first output transistor coupled to the supply voltage, maintaining a constant voltage across the first output transistor using a second output transistor coupled between the first output transistor and an output node, modulating a compensation impedance between a first node and ground as the supply voltage varies, the first node located where the first output transistor is coupled to the second output transistor, and wherein the modulating includes modulating the compensation impedance to substantially equal an output impedance, the output impedance measured between an output node and an input for the supply voltage.