Base Current Cancellation Circuit for Linear CTAT Generation
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Solution Overview
Problem
Bandgap reference circuits face challenges in generating stable reference voltages at low voltage, low power, and extended temperature ranges due to non-linear base current relationships with temperature, affecting the accuracy of CTAT current generation in deep submicron technologies.
Innovation Solution
The implementation of base current cancellation circuitry on a semiconductor IC, which provides a linear CTAT current relationship with temperature by minimizing the effects of non-linear base current relationships, using a combination of P-channel and N-channel transistors and bipolar junction transistors to generate CTAT current, and a compensation circuit to ensure accurate temperature-independent performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional bandgap reference circuits are used in deep submicron technologies, then manufacturing process compatibility is maintained, but base current non-linearity with temperature degrades CTAT current generation accuracy
Solution Approach 1:
The patent extracts and separately compensates for the base current component from the total current in the CTAT circuit. By identifying and removing the non-linear base current effect through a dedicated cancellation circuit, the remaining current more accurately represents the desired CTAT relationship, thereby improving measurement precision while maintaining manufacturing compatibility
Solution Approach 2:
The patent implements a feedback mechanism where the base current cancellation circuit continuously monitors and compensates for base current variations. The cancellation circuit uses feedback from the operating conditions to adjust and counteract the non-linear base current effects, maintaining accurate CTAT current generation across temperature variations
2Measurement precision
If base current cancellation circuitry is added to improve CTAT current accuracy, then temperature relationship linearity is improved, but circuit complexity increases
Solution Approach 1:
The patent merges the base current cancellation functionality with the existing bandgap reference circuit architecture. By integrating the cancellation circuitry into the overall reference voltage generation system rather than adding it as a completely separate module, the patent achieves improved CTAT current accuracy while minimizing the increase in overall circuit complexity
Solution Approach 2:
The base current cancellation circuit is designed to perform multiple functions within a unified structure. It simultaneously compensates for base current non-linearity, maintains temperature-independent operation, and works across various operating conditions, thereby achieving improved precision without proportionally increasing complexity
3Use of energy by moving object
If conventional CTAT current generation is used at low voltage, then power consumption is reduced, but base current effects become more significant and degrade accuracy
Solution Approach 1:
The patent introduces an intermediary base current cancellation circuit that mediates between the low voltage operating conditions and the accuracy requirements. This intermediary circuit actively compensates for the enhanced base current effects that occur at low voltage, allowing the system to maintain both low power consumption and high reference voltage accuracy
Data Source
AI summary
An integrated circuit includes a base current cancellation circuit and a complementary to absolute temperature (CTAT) circuit. The base current cancellation circuit includes a first bipolar junction transistor (BJT) and a current mirror coupled to the first BJT. The current mirror is configured to provide a mirrored current to a base electrode of the first BJT. The CTAT circuit is coupled to receive a voltage signal corresponding to a reference current of the current mirror. The CTAT circuit includes a second BJT coupled to form a base current based on the voltage signal.