Comments on: Variable Power Supply using LM317 Voltage Regulator

By: jugi63

jugi63 — Mon, 04 Feb 2019 08:11:47 +0000

Hi there!
Any reason why no to add additional capacitance to the output to filter and maybe make better sound with audio applications?

Thanks!

By: Chris N

Chris N — Tue, 26 Jun 2018 17:05:17 +0000

In reply to biloa florentgabin.

No.

C1 needs to be an electrolytic capacitor, which has a high capacitance, here 2200 uF. Unfortunately such capacitors have a poor high frequency performance, so C2 is added – typically a ceramic capacitor, which has a very good high frequency performance. A much lower value, is needed – here 0.33 uF – more usually written as 330 nF.

By: biloa florentgabin

biloa florentgabin — Mon, 04 Jun 2018 16:08:37 +0000

Hello, please I wish to know if C1 and C2 can be merge to C, where C = C1+C2 ?
Thank you.

By: tropicalspeed

tropicalspeed — Tue, 22 May 2018 11:58:36 +0000

In reply to Milind Sutar. that is the voltage required by the Adjust terminal to create the equilibrium required by the regulator. So, whatever the choice of output voltage, in order to attain that, the Adjust terminal has to see 1.25VDC. You see, the voltage applied to the Adjust terminal is compared (by a comparator) to an internal preset 1.25 reference voltage. An error occurs whenever the two are not the same. The regulator will make adjustments to the output until the two are back into "equilibrium."That is regulation and it is what makes these 3-terminal devices so simple to setup.

By: Md Gouse Niyazi

Md Gouse Niyazi — Mon, 09 Oct 2017 04:00:00 +0000

How to design 3-12V regulated variable dc power supply?

By: Milind Sutar

Milind Sutar — Tue, 26 Sep 2017 02:34:00 +0000

What is that 1.25 in Voutput equation?

By: Waleed Bin Tariq

Waleed Bin Tariq — Tue, 28 Feb 2017 05:21:00 +0000

i made center tapped arrangement using a center tapped transformer 10-0-15 i got 16 volts maximum as output from dc supply why i cannot get 24 volts?
and plz tell me why we are using two diodes with LM317T?

By: Alexandr Chekmarev

Alexandr Chekmarev — Sat, 11 Feb 2017 13:35:00 +0000

—===It is also clear from the data sheet that
the worst case scenario dropout voltage for the LM317 is almost 2.3 V.
So, to be in the safe side it is advisable to select a transformer
with at least 4V greater than the required output voltage(2.3V of 317 +
1.4V of bridge rectifier). ===—

If I select a transformer with an output voltage of 25 volts AC, the output from the diode bridge and get Capacitors C1 ~ 33 volts with no load. In this case, I can use the LM317T. And if a 36 volt AC outlet for the transformer, after the diode bridge and a capacitor C1, I get ~ 49 volts with no load. In this case, I can not use LM317T?

By: Ligo George

Ligo George — Thu, 02 Jun 2016 13:09:00 +0000

In reply to Mohsin. It is the ripple voltage. AC content in the output.

By: Mohsin

Mohsin — Sat, 21 May 2016 17:26:00 +0000

What is Vr in the formula ?