voltage regulator LM 723 ?

Hi,

Input 24 vac, throw full rectifier with 1000 UF capacitor. Achieved 7 to 30 vdc output. Used less than a 2 watt load for the test.

I have never built a circuit board before. I am focusing on the regulator. I found this schematic and built it. It works, and then I studied it. It seems that the voltage regulator watches terminal #4 voltages input, mine is 7 Volts. If the voltage drops at terminal #4, the regulator increases voltage out terminal #10 until 7 volts is found again at terminal #4. Is this correct?


Thank you

Hi,
Lm723 regulator ic once was a legend now pretty much outdated by modern regulators but still used and widely available.
Pin 4 is the non-inverting input of the operational amplifier inside the regulator. 20K variable resistor is connected between ground and output,acts as voltage divider through its viper which is connected to pin 4 of regulator.
The voltage sensed at the viper of variable resistor is fed to op-amp which controls the output level at pin 10.
This is the simplest way it could be described other wise technical way is not so simple.
Please download the datasheet for the ic and you will be at ease to understand much better.The link for datasheet is here.
LM723 Datasheet catalog
The circuit you posted is very basic.Many safety features can still be added.And output voltage can be brought to 0v at lowest setting of 20k VR by connecting the pin 7 of ic to negative voltage from -3.3v to -5v. But with your circuit it will also reduce the max output voltage limit.

HI lomode,
yes that is correct and your observation is nice. This circuit is just a beginning. If you are interested for more circuits for getting experience let me know I may guide you further.

Thank you.
Rasa, that would be much appreciated. I will look forward to your answers.
Thank you very much.

HI logmode,
here is a beautiful adjustable supply circuit from 0~30 volts with 3 amps current. The series pass transistor is a Darlington and should be mounted on an appropriate heat sink. Transformer 230V and 5 ampere current will do. The smoothing capacitor is capable for supplying any large current by load demand up to 3 amps. It works fine in my lab.

I am pasting another circuit but the problem is main regulating device (a MOSFET BUK116-50L) is not available any more. Though a replacement is available from Digikey but but with a lower current rating. Anyways here is the circuit.
View attachment POWER-SUPPLY-SCH.pdf
Enjoy.....................!

Hi,
The second supply posted by RAZA is a laboratory grade supply.I made it both with original Buk116-50(found by chance at electronics store) and with common 3-pin Mosfet with same current and voltage ratings.I just did not build the circuit at pins 2 and 4.Every thing else works just fine.
Here is double sided board just to get the idea if some one wants to build this supply on double sided board.Its for original circuit with BUK116-50 which is SMD version of mosfet.

Here's a bit of useful trivia (is that an oxymoron?) regarding the 723: It was developed by Fairchild Semiconductor. Unfortunately, the pinout designation in the Fairchild catalog was incorrect. I don't remember what the error was, but if you connected it in accordance with their spec sheet, it would be destroyed. If you run across one of Fairchild's original spec shetts, burn it!