Abstract
A high precision temperature compensated CMOS bandgap reference is presented. The proposed circuit employs current-mode architecture that improves the temperature stability of the output reference voltage as well as the power supply rejection when compared to the conventional voltage-mode bandgap referenc. Using only first order compensation the new architecture can generate an output reference voltage of 550mV with a peak-to-peak variation of 400μV over a wide temperature range from -25 o C to +100 o C which corresponds to a temperature coefficient of 5.8ppm/oC. The output reference voltage exhibits a variation of 2.4mV for supply voltage ranging from 1.6V to 2.0V at typical process corner. A differential cascaded three-stage operational amplifier is included in the bandgap circuit to improve the power supply rejection of the BGR. Simulation result shows that the power supply rejection ratio of the proposed circuit is 79dB from DC up to 1kHz of frequency. The proposed bandgap reference is implemented using UMC 0.18μm CMOS process and it occupies an active layout area of 0.14mm 2 .
Highlights
Bandgap reference (BGR) is an important building block which is required in many analog and mixed-signal systems such as communication systems and data acquisition systems, as well as some digital systems such as dynamic random access memories (DRAMs)
The operational amplifier used in the proposed BGR circuit gives a gain of 62dB and a phase margin of 80 degree which are enough for this application
The power supply rejection ratio (PSRR) Vs. frequency plot is shown in Figure 8, from which it can be found that PSRR of the proposed BGR is 79dB at typical process corner at 27oC at low frequency and is stable up to
Summary
Bandgap reference (BGR) is an important building block which is required in many analog and mixed-signal systems such as communication systems and data acquisition systems, as well as some digital systems such as dynamic random access memories (DRAMs). A good bandgap reference circuit is required to have a high power supply rejection ratio (PSRR) and a very low temperature coefficient (TC) over a large temperature range. Conventional BGR architecture [5] employs voltage-mode to produce a stable voltage reference. The proposed architecture incorporates current-mode operation, where two currents having complementary type TC are added to generate a temperature independent current and thereby, producing a temperature independent voltage reference. Compared to the traditional BGR circuit , the proposed circuit can produce reference voltages less than 1.2V to meet the requirements of designs under low supply voltages. With the help of resistors and bipolar transistors, the proposed circuit can produce a very low TC of Vref with only first-order temperature compensation. As there are no high-order curvature compensations employed, the structure of proposed circuit greatly reduces the circuit complexity. The Miller compensation technique is incorporated in the opamp circuit to improve the stability of the circuit
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