1) Pin configuration of IC 723 :
2) Functions of each pin:-
V+ and V-: These are the supply voltage terminals of the IC. V+ is the positive terminal and V- is the negative terminal.
Non Inverting Input: This is the non-inverting input of the error amplifier whose output is connected to the series pass transistor. Reference voltage or a portion of it is given to the noninverting input.
Inverting Input: This is the inverting input of the error amplifier whose output is connected to the series pass transistor. Usually output voltage or a portion of it is given to the inverting input. This makes the output voltage constant.
Vref: It is the reference voltage output of the IC. It is the output of voltage reference amplifier. Its output voltage is about 7.15V.
Vout : It is the output terminal of the IC. Usually output voltage ranges from 2 to 37V. This pin can provide up to 150mA current.
Current Limit: It is the base input of the current limiter transistor. This pin is used for current limiting or current fold back applications.
Current Sense: This is the emitter of current limiting transistor. This terminal is used with current limiting and current fold-back applications.
Vc : This is the collector input of the series pass transistor. It is usually directly connected to the positive supply voltage if an external transistor is not used.
Freq. Comp: Frequency Compensation : This pin is used to connect a capacitor which bypasses high frequency noises. It is the output of error amplifier. The capacitor is connected between this pin and inverting input of the error amplifier. The prescribed value of this capacitor varies for different types of regulators.
Current Sense: This is the emitter of current limiting transistor. This terminal is used with current limiting and current fold-back applications.
Vc: This is the collector input of the series pass transistor. It is usually directly connected to the positive supply voltage if an external transistor is not used.
Freq. Comp: Frequency Compensation: This pin is used to connect a capacitor which bypasses high frequency noises. It is the output of error amplifier. The capacitor is connected between this pin and inverting input of the error amplifier. The prescribed value of this capacitor varies for different types of regulators.
Vz: It is the anode of the zener diode whose cathode connected to the output terminal. It is usually used for making negative regulators.
3) Circuit diagram for obtaining 6V output d.c. regulated voltage using IC 723
Expression Vout = Vref * (R2 / R1+R2)
Assume any value of R2, R1 can be calculated.