Start-up circuit of bandgap reference circuit

By introducing an inverter and switching control into the bandgap reference circuit, the degeneracy problem at the positive and negative input terminals of the operational amplifier is solved, the stable establishment of the reference voltage and the maintenance of the temperature coefficient are achieved, and the stability and accuracy of the circuit are improved.

CN122308548APending Publication Date: 2026-06-30SHANGHAI HUALI INTEGRATED CIRCUIT CORP
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
SHANGHAI HUALI INTEGRATED CIRCUIT CORP
Filing Date
2026-03-27
Publication Date
2026-06-30

AI Technical Summary

Technical Problem

When the existing bandgap reference circuit is powered on, the positive and negative input terminals of the operational amplifier may become degenerate, causing the output voltage to oscillate or fail to establish properly, and affecting the temperature coefficient and accuracy of the output voltage.

Method used

An inverter, a first switch, and a second switch are introduced into the main circuit of the bandgap reference circuit. By controlling the on and off states of the switches, the output of the operational amplifier is pulled down in concert to ensure that the voltage at the negative input terminal is higher than that at the positive input terminal, thus avoiding the occurrence of degeneracy and maintaining the temperature coefficient of the reference voltage unchanged after power-on.

Benefits of technology

It effectively eliminates the competition at the output of the operational amplifier, prevents reference voltage oscillation, ensures that the reference voltage is stably established during power-on, and maintains that the temperature coefficient is unaffected after completion, thereby improving the accuracy of the output voltage.

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Abstract

This invention discloses a startup circuit for a bandgap reference circuit. The startup circuit includes an inverter and first and second switches. A second switch is placed in a second resistor path between the negative input terminal of the operational amplifier in the main circuit of the bandgap reference circuit and ground. Upon power-up, before the reference voltage rises to the switching voltage of the inverter in the startup circuit, the first switch is turned on, pulling down the output of the operational amplifier. The second switch is turned off, making the voltage at the negative input terminal of the operational amplifier higher than the voltage at the positive input terminal, thus collaboratively pulling down the output of the operational amplifier. After the reference voltage rises to the switching voltage of the inverter, the first switch is turned off, and the second switch is turned on. This invention eliminates the simplification of the input state of the operational amplifier during power-up and the resulting competition between pull-up and pull-down voltages at the output terminal, thus eliminating the oscillation or even failure to establish the reference voltage. Furthermore, it ensures that the temperature coefficient of the reference voltage remains unaffected after power-up.
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