Differential Bandgap Reference Circuit With Flicker Noise Compensation
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Solution Overview
Problem
Conventional current-mode bandgap reference voltage generator circuits suffer from flicker noise introduced by MOSFETs, which is problematic for noise-sensitive applications like analog-to-digital converters, and existing solutions like the chopper technique complicate circuitry and require a stable clock source.
Innovation Solution
A differential voltage reference generator circuit utilizing bipolar transistors and an operational transconductance amplifier in a current control feedback loop, with a compensation current sink circuit to address flicker noise, and a transresistance amplifier circuit with feedback resistors to manage base currents, ensuring a flicker noise-free output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MOSFETs are used in the current mirroring circuit, then the circuit can be implemented with standard semiconductor devices, but flicker noise is introduced which degrades performance in noise-sensitive applications
Solution Approach 1:
The patent changes the device type parameter from MOSFET to bipolar transistor in the current mirroring circuit. Bipolar transistors inherently generate less flicker noise compared to MOSFETs, thus improving the noise performance of the reference voltage generator while maintaining standard semiconductor implementation.
2Reliability
If the chopper technique is used to reduce flicker noise, then noise performance improves, but circuit complexity increases and a stable clock source is required
Solution Approach 1:
The patent extracts and eliminates the need for chopper stabilization circuitry and clock sources by using bipolar transistors in the current mirroring circuit. The inherent low flicker noise characteristic of bipolar transistors removes the requirement for additional noise-reduction circuitry, thereby simplifying the overall circuit design.
3Reliability
If bipolar transistors are used in the current mirroring circuit, then flicker noise is reduced, but base currents must be compensated which increases circuit complexity
Solution Approach 1:
The patent employs feedback mechanisms through the operational transconductance amplifier to compensate for base currents in the bipolar transistor current mirroring circuit. The OTA continuously adjusts the output to maintain accuracy despite base current effects, achieving noise reduction while managing the complexity through intelligent feedback control rather than additional compensation circuitry.
Data Source
AI summary
A bandgap voltage generator circuit is formed using only bipolar transistors. The bandgap voltage generator circuit includes output nodes generating first and second bandgap reference currents. A transconductance amplifier circuit in a current control feedback loop of the bandgap voltage generator circuit has differential inputs which receive base currents. A differential amplifier circuit has inputs configured to receive the first and second bandgap reference currents and includes a compensation current sink circuit configured to sink compensation currents from the first and second bandgap reference currents which correspond to the base current received at the differential inputs of the transconductance amplifier circuit.