Bandgap Reference Circuit Using Constant Base Current Bias
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Solution Overview
Problem
Process variations in bipolar junction transistors (BJTs) during manufacturing lead to inconsistencies in base-emitter voltage (VBE) and current gain (β), affecting transistor performance and reliability, complicating design optimization and yield.
Innovation Solution
Maintaining a constant base current (IB) instead of a constant collector current (IC) in bipolar junction transistors to mitigate the impact of process variations on VBE, using a first and second transistor to provide a restored bandgap voltage reference that is less sensitive to process variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transistors are manufactured using standard fabrication processes, then production efficiency and cost are maintained, but process variations cause inconsistencies in VBE and β parameters
Solution Approach 1:
The patent changes the biasing parameter from constant collector current to constant base current. By controlling the base current instead of the collector current, the circuit becomes less sensitive to process variations in β while maintaining the desired VBE characteristics. This parameter change allows standard fabrication processes to be used while achieving better parameter consistency.
2Ease of operation
If constant collector current is used to bias the transistor, then the circuit operation is simplified, but VBE varies significantly with process variations
Solution Approach 1:
The patent changes the independent bias parameter from collector current to base current. Since base current is less affected by β variations, this parameter change improves VBE stability while maintaining relatively simple circuit operation. The constant base current approach provides a more reliable reference voltage.
3Manufacturing precision
If process variations are reduced through tighter manufacturing controls, then VBE consistency improves, but manufacturing cost and complexity increase
Solution Approach 1:
Rather than tightening manufacturing controls, the patent changes the circuit's biasing parameter from collector current to base current. This parameter change makes the circuit inherently less sensitive to process variations, achieving better VBE consistency without increasing manufacturing complexity or cost.
4Ease of manufacture
If standard BJT biasing with constant collector current is used, then design is straightforward, but VBE is highly sensitive to β variations
Solution Approach 1:
The patent changes the biasing parameter from collector current to base current. This simple parameter change reduces the coupling between β variations and VBE, improving performance consistency while maintaining straightforward design and implementation.
Data Source
AI summary
An electronic device is provided, including: a terminal configured for receiving a bandgap voltage reference, generated by incorporating a first base-emitter voltage subject to process variation; the electronic device including a first transistor with a base configured to be exposed to the bandgap voltage reference; the first transistor is biased with a constant collector current corresponding with the first base-emitter voltage, and is configured for providing a shifted voltage, VE, based on decreasing the bandgap voltage reference by a second base-emitter voltage subject to the process variation; and the electronic device including a second transistor, of the same type as the first transistor, including an emitter configured to be exposed to the shifted voltage; and the second transistor is biased with a constant base current and is configured for providing a restored bandgap voltage based on increasing the shifted voltage by a third base-emitter voltage.