Bandgap Reference Voltage Circuit Offset Compensation
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Solution Overview
Problem
Existing bandgap circuits in semiconductor integrated circuits face limitations due to the offset voltage of CMOS operating amplifiers, which affect the precision of the reference voltage generated, leading to fluctuations and reduced accuracy.
Innovation Solution
Incorporating an offset adjustment-use auxiliary amplifier and an offset adjustment voltage generation circuit, which divides the bandgap output voltage and adjusts the gate voltages of the main amplifier's transistors to cancel out the offset voltage, thereby improving the precision of the reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a bandgap circuit is used to generate a reference voltage, then temperature stability is improved, but offset voltage from the CMOS amplifier reduces measurement precision
Solution Approach 1:
An auxiliary amplifier is introduced as an intermediary component between the main amplifier and the output node. This auxiliary amplifier detects the offset voltage of the main amplifier and generates a compensating signal that cancels the offset effect, thereby improving reference voltage precision without compromising temperature stability
Solution Approach 2:
The auxiliary amplifier creates a feedback mechanism that continuously monitors the offset voltage of the main amplifier and adjusts the output accordingly. By feeding back the offset information and generating compensating signals, the system automatically corrects precision errors while maintaining the temperature-stable bandgap reference voltage
2Measurement precision
If the offset voltage is reduced by adding an auxiliary amplifier, then reference voltage precision is improved, but device complexity increases
Solution Approach 1:
The auxiliary amplifier is integrated into the existing bandgap circuit architecture, sharing common nodes and power supply connections with the main amplifier. This merging approach allows offset compensation functionality to be added without proportionally increasing overall circuit complexity, as the auxiliary amplifier utilizes existing circuit resources
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
This approach significantly reduces the impact of offset voltage on the bandgap reference voltage, achieving a more stable and precise output voltage with reduced errors, enhancing the accuracy and reliability of the bandgap circuit.
Implementation Method 1
the potential of a forward-biased pn junction (if approximating the potential of the pn junction by a linear equation or within the range able to be approximated by a linear equation) is the CTAT (complementary-to-absolute temperature)
Implementation Method 2
a voltage proportional to the absolute temperature (T) (in general, called PTAT)
Data Source
AI summary
A reference voltage circuit includes a first amplifier configured to output a reference voltage, a second amplifier coupled to the first amplifier, an offset adjustment voltage generation circuit, a first load device and a first pn junction device, and second and third load devices and a second pn junction device. The offset adjustment voltage generation circuit is configured to generate a voltage which is input to the third and fourth input terminals of the second amplifier, and reduce an offset voltage between the first and second input terminals of the first amplifier through the second amplifier. The first input terminal is coupled to a coupling node of the first load device and the first pn junction device, and the second input terminal is coupled to a coupling node of the second load device and the third load device.