Bandgap Voltage Reference Circuit Low Power CMOS Operation
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Solution Overview
Problem
Existing bandgap voltage reference circuits face challenges in operating at low power supply voltages due to inadequate voltage headroom, leading to errors and increased complexity, especially when using parallel architectures that require separate compensation and trimming.
Innovation Solution
The implementation of insulated gate field effect transistors with low threshold voltages and voltage clamp circuitry to stabilize the bandgap voltage reference, ensuring operation across a wide range of power supply voltages while minimizing offsets and trimming requirements, using the Brokaw Architecture with current mirror and bandgap reference circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a parallel architecture bandgap reference circuit is used to operate at low power supply voltages, then voltage headroom is reduced, but circuit errors increase and complexity increases due to separate compensation and trimming requirements
Solution Approach 1:
The patent merges the PTAT current generation and VBE current generation into a single series architecture path, eliminating the need for separate compensation loops. The Brokaw cell integrates multiple functions (current mirroring, voltage generation, temperature compensation) into a unified structure that reduces errors and trimming requirements while maintaining low voltage operation capability
2Measurement precision
If bandgap trimming is used to improve bandgap accuracy, then manufacturing precision is improved, but device complexity increases and productivity decreases due to longer test times
Solution Approach 1:
The circuit employs self-compensating mechanisms through the series architecture and Brokaw cell design, where temperature drifts and process variations automatically cancel each other out. This self-service approach eliminates the need for external trimming components and post-fabrication adjustment mechanisms, reducing both circuit size and test time while maintaining high accuracy
3Reliability
If voltage protection circuitry is added in series with PMOS devices to protect from voltage variations, then reliability is improved, but device complexity increases and operation at low VDD is limited
Solution Approach 1:
The patent changes the operating parameters of the PMOS devices by selecting low threshold voltage variants and operating them in the triode region rather than saturation. This parameter change allows the devices to withstand higher voltage variations without requiring additional protection circuitry, maintaining reliability while reducing complexity and preserving low voltage operation capability
Data Source
AI summary
Bandgap voltage reference circuitry capable of operating at very low power supply voltages. The current source for driving the core bandgap voltage reference is implemented with insulated gate field effect transistors having low threshold voltages. Voltage clamp circuitry protects the transistors from power supply voltage variations rising above a predetermined clamp voltage. An output amplifier with output biasing circuitry having a circuit structure similar to that of the core bandgap voltage reference ensures that the bandgap reaches the intended steady state of operation.