# Precise line regulation using linear voltage regulators

I am trying to build a linear 24/12V power supply. One of the requirement for it is for the line regulation to be very precise (an error of 0.0005 V is considered acceptable). I wanted to use a linear regulator Ic, but I haven't found any that fit my needs.

What can I use to build such a supply?

Thanks!

• You're asking for +/-20ppm. Why? What do you know about precision analog design? Line regulation wouldn't mean much if it shifts with temperature, would it? – Spehro Pefhany Nov 24 '16 at 0:59
• How much current do you want to pull from this thing? And does it need to sink current as well as source it? – ThreePhaseEel Nov 24 '16 at 1:08
• Well, you certainly can't use any existing regulators. As Spehro has pointed out, your requirement is quite extreme. Are you aware that a fairly normal resistor tempco is 100 ppm/deg C? – WhatRoughBeast Nov 24 '16 at 2:09
• Please specify: (1) the load current; (2) the output voltage: is it 12 V, or 24 V, or both? (3) temperature stability requirements. – Master Nov 24 '16 at 8:51
• @Master The load current is 250 mA max. The output voltage is 12V. temerature stability is as follows: 20C - 12.0198 V 25C - 12.0195 V 40C - 12.0190 V – Egor Tamarin Nov 26 '16 at 12:24

If your goal is less supplying power and more a precise voltage, consider a precision voltage reference. These can be as cheap as $5 if you're willing to buy from china. In conclusion: • Linear power supplies step down voltage with considerable ripple based on many factors, like supply voltage, and also produce heat • This heat makes them a poor choice for situations requiring high voltage, long battery life, or both. • A switch mode power supply may be good if you can find one with that precision if you still want efficiency • Also, consider a precision voltage reference if you need very high precision. • Sorry for not clarifying. I am trying to do it from a 24V DC. I'm a student, and I ahve a project underway where I have to build both a switching supply and a linear one - I myself would have built a second switching one if only the task allowed me to do that. – Egor Tamarin Nov 26 '16 at 12:21 • Ok. Egor, is that precision required? And you say you must make both a linear and switching supply on your own/from scratch? I would assume with this new info that a precision voltage reference would not work - you are trying to specifically make power supplies. Is that precision really necessary? – Bobdabiulder Nov 26 '16 at 12:59 • I read the above comments. This sounds like a very hard task. Is there any more info you can provide? – Bobdabiulder Nov 26 '16 at 13:01 • Well, I asked the project supervisor and he said that no IC's will do the job. Yes, the precision is required. Additional info: For line regulation the specs are: Vin 15 V - Vout 12.0188V Vin 17 V - Vout 12.0182 V Vin 20 V - Vout 12.0185 V at Iout = 125 mA For load regulation at 17 V: Vout = 12.0215 V - Iout = 0mA Vout 12.0185 V - Iout 125mA Vout 12.0155 V - Iout 250mA – Egor Tamarin Nov 26 '16 at 14:56 • Huh. Maybe a voltage divider with hugh precision resistors. You can get 600 +/- 1% resistors of 30 different values for$5 from china, but you might need more precision than that. – Bobdabiulder Nov 26 '16 at 15:07