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In this paper, design of a voltage reference circuit using only MOS transistors and without employing an operational amplifier is presented. A proportional to absolute temperature [PTAT] voltage and a PTAT current are designed then difference of the PTAT voltage and product of the PTAT current and resistor gives the temperature independent voltage. The advantages of both sub-threshold and strong inversion region operation of MOS transistors are exploited in the design. The voltage reference is implemented using standard CMOS 180 nm technology. The voltage reference provides a voltage of 224.3 mV consuming a quiescent current of 30 μA at room temperature. Post layout simulation results show that the proposed voltage reference has a temperature coefficient of 167.18 ppm/°C and varies only 3mV when there is a ±10% variation in supply voltage. The circuit occupies an area of only 93.6×32.6μm on the chip, making it suitable for area constraint applications.

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An area efficient output capacitor-free low dropout [LDO] voltage regulator with an improved figure of merit is presented in this paper. The proposed LDO regulator consists of a novel, dynamically biased error amplifier that reduces overshoot and undershoot voltage spikes arising from abrupt load changes. Source bulk modulation is employed to enhance the current driving capability of the pass transistor. An adaptive biasing scheme is also used along with dynamic biasing to improve the current efficiency of the system. The on-chip capacitor required for proper working of the LDO regulator is only 35 pF. The proposed LDO regulator is designed and simulated in 180 nm standard CMOS technology. The LDO regulator exhibits a line regulation of 1.67 mV / V and a load regulation of 100 µV / mA. When load changes from 0 mA to 100 mA in 1 µ s, an undershoot of 148 mV and an overshoot of 172 mV are observed. The measured power supply rejection ratio is 25 dB at 100 kHz. The working of the proposed LDO regulator has been tested under all process corners and Monte-Carlo statistical analysis reveals that it is robust against process variations and local mismatch.