| Summary: | 碩士 === 國立虎尾科技大學 === 電子工程系碩士班 === 106 === This paper has proposed four different reference voltage circuits which are suitable for portable devices. Without using BJT transistors to implement both negative temperature-coefficients and positive temperature- coefficient voltages, instead, MOS transistors have been applied to all the proposed circuits. Properly biased the MOSFET in weak-inversion region, both the positive and negative temperature-coefficients parameters can be obtained. After choosing appropriate weightings, a zero temperature-coefficient reference voltage can be realized.
In the studies, all the proposed circuits use TSMC 0.18 m process parameters to make the layout and taped-out. HSPICE circuit simulation program has been used to perform pre- and post-layout simulations. The first two circuits are connected in series with a NMOS and/or PMOS transistor that is used for providing the negative temperature-coefficient voltage. For the latter two circuits, a P-type transistor and an N-type transistor is connected between the transistors that used to generates the positive temperature coefficient and ground, respectively.
According to the pre-layout simulation results, when the supply voltage is 1.8V, the bias voltage varies from 0.39V to 0.45V, and the temperature changes from -20oC to 120oC, the variation of the output voltage of the N-type modified circuit is lower than the P-type one. The proposed circuit is simple, and the power consumption of all the four circuits is less than 10 mW. From the simulation results, it can be seen that the simulation results are consistent with the theoretical derivation, which also proves the feasibility of the design principle. The reference voltage circuits proposed in this paper can be applied to various related analog integrated circuits and other portable devices.
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