1.5V LDO voltage regulator. The LED provides a voltage reference. The NPN transistor is the error amplifier and the PNP transistor is the pass transistor. 30 ohm resistor represent the output load. Load regulation is around +/- 7% max o/p current 50mA. If you're going to build this I'd the 100uF capacitor across the output is essential for stability, otherwise it could be likely to oscillate. The LED resistor needs to be increased with higher input voltages, otherwise the reference voltage is too high and in turn the output will be too high.
I breadboarded this circuit today (15-6-17) and it actually works quite well, performance improves considerably when the input voltage is greater or equal to 5 volts.
