Calibration of Offset Voltage of Op-Amp for Bandgap Voltage Reference Using Chopping Technique and Switched-Capacitor Filter
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A calibration scheme is proposed for a bandgap voltage reference. The proposed scheme calibrates an offset voltage of operational amplifier (op-amp) of a bandgap reference which is the critical source of an output-voltage deviation of the bandgap reference. The proposed calibration is based on a chopping technique which makes an output voltage of op-amp modulate. An IIR filter is used to average out the modulated output voltage of chopped amplifier. The output voltage of IIR filter is fed into gate node of a PMOS current source which is located in the final output branch. As a result, the output reference voltage becomes insensitive to the offset voltage of op-amp. The proposed circuit was verified through Monte-Carlo simulations by using thick-oxide transistors in a 0.13-m CMOS process. In the simulation results, the proposed calibration suppresses the deviation of output reference voltage up to 1.94 mV for the temperature range between -40oC and 125oC. Also, the deviation of output reference voltage is reduced by 24.5 times through proposed calibration.
Abstract
A calibration scheme is proposed for a bandgap voltage reference. The proposed scheme calibrates an offset voltage of operational amplifier (op-amp) of a bandgap reference which is the critical source of an output-voltage deviation of the bandgap reference. The proposed calibration is based on a chopping technique which makes an output voltage of op-amp modulate. An IIR filter is used to average out the modulated output voltage of chopped amplifier. The output voltage of IIR filter is fed into gate node of a PMOS current source which is located in the final output branch. As a result, the output reference voltage becomes insensitive to the offset voltage of op-amp. The proposed circuit was verified through Monte-Carlo simulations by using thick-oxide transistors in a 0.13-m CMOS process. In the simulation results, the proposed calibration suppresses the deviation of output reference voltage up to 1.94 mV for the temperature range between -40oC and 125oC. Also, the deviation of output reference voltage is reduced by 24.5 times through proposed calibration.
참고문헌 (10)
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