Soft Turn-ON BJT-Boosted Zener Reference Voltage Regulator

This is a Zener voltage regulator with NPN series pass transistor, the circuit includes a turn-on delay. Turn-on delay is accomplished through Q2 and the delay capacitor Cdelay. When the circuit is turned on the Zener diode does not work immediately because its cathode is pulled down through transistor Q2 by the low voltage of the capacitor Cdelay. As the capacitor charges up the voltage at the anode of the Zener diode rises up eventually enabling the diode to work as a voltage regulator. With the saved values the turn-on delay is about 1.25 sec.