Functions of IC 723 : 1. Series, shunt, switching and floating regulators 2. Basic Low-voltage Regulator (Vo = 2 to 37 volts) 3. Low Voltage High Current Regulator.
Block diagram explanation : Temperature compensated zener diode, constant current source and reference amplifier constitutes the reference element. In order to get a fixed voltage from zener diode, the constant current source forces the zener to operate at a fixed point. Output voltage is compared with this temperature compensated reference potential of the order of 7 volts. Error amplifier is high gain differential amplifier. It’s inverting input is connected to the either whole regulated output voltage or part of that from outside. For later case a potential divider of two scaling resistors is used. Scaling resistors help in getting multiplied reference voltage or scaled up reference voltage. Error amplifier controls the series pass transistor Q1, which acts as variable resistor. The series pass transistor is a small power transistor having about 800 mW dissipation. The unregulated power supply source (< 36V d.c.) is connected to collector of series pass transistor. Transistor Q2 acts as current limiter in case of short circuit condition. It senses drop across lc placed in series with regulated output voltage externally.
The frequency compensation terminal controls the frequency response of the error amplifier. The required roll-off is obtained by connecting a small capacitor of 100 pF between frequency compensation and inverting input terminals.