Beta-Compensated BJT Reference Voltage for PVT Stability
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Solution Overview
Problem
Existing technologies face challenges in generating a process, voltage, and temperature (PVT) invariant reference voltage due to the non-linear variations in the beta value of bipolar junction transistors (BJTs), particularly when manufactured using CMOS technology, which results in low beta values and non-linear base-emitter voltage changes with temperature.
Innovation Solution
A circuit and method are developed to generate a PVT invariant reference voltage by combining a CTAT base-emitter voltage with a PTAT voltage, using a beta-compensated current generation circuit to negate the non-linear effects of the beta value, involving a beta-compensated current generation circuit and a PTAT current source, which is inversely proportional to the beta value of the BJT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a BJT is used to generate reference voltage, then the base-emitter voltage provides temperature compensation, but the non-linear beta value causes non-linear base-emitter voltage changes
Solution Approach 1:
The patent introduces a beta-compensated current generation circuit as an intermediary component that processes the PTAT current to produce a beta-compensated current. This intermediary circuit uses operational amplifiers and transistors to actively compensate for beta variations, thereby linearizing the base-emitter voltage changes while preserving the temperature compensation property.
Solution Approach 2:
The patent changes the current parameter by generating a beta-compensated current that is inversely proportional to the beta value. By adjusting the current through the BJT using the beta-compensated current, the non-linear effects of beta variations are counteracted, resulting in more linear base-emitter voltage characteristics.
2Ease of manufacture
If CMOS technology is used to manufacture BJT, then integration is improved, but beta value becomes low and non-linear
Solution Approach 1:
The patent implements feedback through the beta-compensated current generation circuit that continuously monitors and adjusts the current based on temperature variations. The circuit uses operational amplifiers to provide negative feedback, ensuring that the beta-compensated current accurately compensates for beta variations, thereby maintaining reliable reference voltage generation despite low beta values in CMOS-manufactured BJTs.
3Manufacturing precision
If beta-compensated current generation circuit is added, then non-linear effects are reduced, but circuit area increases
Solution Approach 1:
The patent applies partial compensation by generating a beta-compensated current that specifically targets the non-linear effects without fully redesigning the entire reference voltage generation circuit. The beta-compensated current is combined with the PTAT current in a controlled manner, providing sufficient linearization while avoiding the excessive area that would result from a complete circuit redesign.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution stabilizes the reference voltage across varying processes, voltages, and temperatures, improving the reliability and accuracy of electronic devices, especially high-precision temperature sensors, by reducing the error in temperature readings and minimizing circuit area.
Implementation Method 1
a proportional to absolute temperature (PTAT) current source electrically coupled to the emitter terminal of the reference BJT. The PTAT current source may be configured to generate a PTAT current that is proportional to absolute temperature
Implementation Method 2
The base-emitter voltage (VBE) extracted from a BJT is complementary-to-absolute-temperature (CTAT). As a CTAT voltage, the base-emitter voltage decreases near-linearly as temperature increases
Implementation Method 3
an operational amplifier configured to maintain equal voltages at input terminals of the operational amplifier
Implementation Method 4
first p-type metal-oxide-semiconductor field-effect transistor (PMOS) comprising: a drain terminal electrically coupled to the positive input terminal of the operational amplifier; a gate terminal electrically coupled to the output terminal of the operational amplifier
Implementation Method 5
a resistive element having a first terminal and a second terminal, the second terminal electrically coupled to the emitter terminal of the reference BJT
Data Source
AI summary
A circuit and method for generating a PVT invariant reference voltage are provided. The example circuit includes a reference BJT, wherein a ratio of a collector current at the collector terminal and a base current at the base terminal is equal to a beta value. The example circuit further includes a resistive element having a first terminal and a second terminal, the second terminal electrically coupled to the emitter terminal of the reference BJT. A reference voltage is generated by the example circuit based on a voltage difference between the first terminal of the resistive element and the base of the reference BJT. The example circuit further includes a beta-compensated current generation circuit configured to generate a beta-compensated current, based on a PTAT current, at the emitter terminal of the reference BJT, wherein the beta-compensated current is inversely proportional to the beta value of the reference BJT.