The UCC381-3/-5/-ADJ family of positive linear series pass regulators is tailored for low drop out applications where low quiescent power is important. Fabricated with a BiCMOS technology ideally suited for low input to output differential applications, the UCC381 will pass 1A while requiring only 0.5V of input voltage headroom. Dropout voltage decreases linearly with output current, so that dropout at 200mA is less than 100mV. Quiescent current is always less than 650A. To prevent reverse current conduction, on-chip circuitry limits the minimum forward voltage to typically 50mV. Once the forward voltage limit is reached, the input-output differential voltage is maintained as the input voltage drops until undervoltage lockout disables the regulator.