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Reference source design and application of low temperature coefficient and high power supply rejection

Author: MouFeiYan
Tutor: TangGuang
School: University of Electronic Science and Technology
Course: Circuits and Systems
Keywords: bandgap curvature compensation temperature coefficient power supply rejection BiCMOS
CLC: TN432
Type: Master's thesis
Year: 2010
Downloads: 99
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Abstract

As a voltage output circuitry, refernces provide bias voltages for integrated circuits; decrease circuits’temperature drift; promote power supply rejection of circuits. With the increasing accuracy of integrated circuits, the performance requirements of a reference are becoming higher. To achieve the needs of modern systems, a reference with low temperature coefficient and high power supply rejection is designed in this paper. Based on the reference, 3 kinds of application circuits are also designed in this paper.In order to achieve low temperature coefficient and high power supply rejection, a classic reference topology is analyzed in detail firstly, and the expression that connects the device perimeter and system specification is obtained to serve for the designing. To reduce the influence of circuit nonidealities, a detailed analysis is also performed and the strategies of devices and circuits’design to diminish the effect of circuit nonidealities are proposed.Secondly, based on the classic reference topology and detailed analysis towards it, a low temperature coefficient reference with high power supply rejection is introduced. A curvature compensation against the nonlinear temperature dependence of the base-emitter junction voltage is performed, and the temperature coefficient of the reference decreases to as low as 0.68ppm/℃. A preregulator with simple topology is designed and with the help of it, the power supply rejection ratio is 130dB, with an improvement of 60dB. A self biased operational amplifier is proposed with reduced input offset. To suppress the circuit noise and high frequency supply noise, a large bypass capacitor is used, and the output referred noise is reduced to 10μVRMS.Three kinds of application of reference are also introduced in this paper: the low dropout regulator, the temperature sensor and the output buffer. To decrease the output overshoot of the regulator, a buffer is incorporated, which results in an overshoot less the 40mV. A reverse Wilder current mirror is used to improve the linearity of the temperature sensor. The simulated linearity is 0.47‰FS. To get a large transconductance, a multistage topology is incorporated. The circuits are designed in a BiCMOS technology. The test results show a good coincidence with the simulation results. The test results also manifest that defects existed in the layout design.

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