Design Of A LDO Linear Voltage Regulator Without External Capacitor

With the fast development of portable electronic products, DC voltage regulators become more and more important. Low dropout(LDO) linear regulators has been applied widely due to its good output stability and small voltage-ripples. However, traditional LDO regulators usually need a large external capacitor, which will increase the cost, to solve this problem, a LDO linear voltage regulator without external capacitor is designedIn this thesis, a folded cascode op-amp is designed. Based on the op-amp, three reference voltage source circuits are designed, which include a traditional bandgap reference voltage circuit, a second-order compensated reference voltage circuit, and an all-MOS reference voltage circuit, and then these reference voltage circuits are simulated and compared. The simulation results show that the performance of the all-MOS reference voltage circuit is best, whose temperature coefficient of bandgap reference voltage is 0.68 ppm/°C, linear adjustment rate is 17.5 μV/V and power consumption is 0.4 mW.Based on the all-MOS reference voltage circuit designed before, this thesis designed and simulated a LDO circuit without external capacitor, using Miller capacitor to compensate the loop. The circuit is powered by a negative supply which scans from-9 to-15 V, and its output voltage is-8 V, its maximum output current is 200 mA, its linear adjust rate is 941 μV/V, its load adjust rate is 0.42 V/A, its temperature coefficient is 78.12 ppm/°C, its power supply rejection ratio at low frequency is-54.36 dB, its power dissipation is 2.9 mW, its transient overshoot voltage is 230 mV, respectively. After all the parameters has met the requirements, the layout of the circuits is designed and delivered to the foundry to tape out.