Could someone help me with a reg. with 0.1-0.5V out - diyAudio
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Old 19th August 2008, 05:47 PM   #1
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Default Could someone help me with a reg. with 0.1-0.5V out

Hello!

I need help to make a regulator that is gonna put out 0.1-0.5V (variable) and gonna accept ~ 8-18VDC in (car battery).

If someone has a schematic I would be grateful

Thanks

/Tobias
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Old 19th August 2008, 06:37 PM   #2
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You do mean one-tenth to one-half a volt, correct?

The key question is how much current you need.
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Old 19th August 2008, 07:22 PM   #3
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Yes correct on the voltage.

Don't really know about the current but I can't think more than 100mA is needed.

It's for a friend that's gonna do something with his car.. like finetuning something in the lambdasond.

Cheers
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Old 19th August 2008, 08:53 PM   #4
lineup is offline lineup  Sweden
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This is the most low cost solution, I could quickly make up.
But still is very precise, if you adjust it to your load.

It is tested with very standard components in my simulator.

At 100 mA load the output voltage is adjustable
between like 0.020 --- 0.530 Volt

Less current output is of course possible, too.
But avoid put out more than 100 mA. (need some modification for this)

Enjoy!
And welcome join my Audio Electronics forum f
or more Lineup stuff & circuits:
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Old 19th August 2008, 10:08 PM   #5
cerrem is offline cerrem  United States
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Quote:
Originally posted by lineup
This is the most low cost solution, I could quickly make up.
But still is very precise, if you adjust it to your load.

It is tested with very standard components in my simulator.

At 100 mA load the output voltage is adjustable
between like 0.020 --- 0.530 Volt

Less current output is of course possible, too.
But avoid put out more than 100 mA. (need some modification for this)

Enjoy!
And welcome join my Audio Electronics forum f
or more Lineup stuff & circuits:
http://lineupaudio.freehostia.com/forum/index.php

It was nice for you to provide this....but i don't see where it has any regulation????
The temp/co of the pot and the delta Vbe of Q1 with load current and temperature will have the output voltage moving all over the place...... the regulation would be like +/- 300% with normal variance......
The question is what is the required regulation and over what load and temperature variation...?

Chris
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Old 20th August 2008, 03:01 AM   #6
star882 is offline star882  United States
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Use a diode as a reference divided down with a variable resistor dividing down the voltage and a transistor driven by an opamp as a buffer.
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Old 20th August 2008, 03:29 AM   #7
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"This is the most low cost solution, I could quickly make up.
But still is very precise, if you adjust it to your load.

It is tested with very standard components in my simulator.

At 100 mA load the output voltage is adjustable
between like 0.020 --- 0.530 Volt

Less current output is of course possible, too.
But avoid put out more than 100 mA. (need some modification for this)

Enjoy!
And welcome join my Audio Electronics forum f
or more Lineup stuff & circuits:
http://lineupaudio.freehostia.com/forum/index.php

Sorry but this circuit cannot provide an output voltage less than approx 0.7VDC (700mV) - the base - emitter forward bias voltage. If you want to use this circuit, you will need a negative supply to provide the proper bias. You can use a PNP in it's place but then it is no longer a follower and you will need to change the topology accordingly.

I you wanted to stick with this follower configuration you could use a rail to rail op-amp buffer (or one with the current output capacity you need) in place of the NPN transistor.
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Old 20th August 2008, 03:40 AM   #8
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Use an LM317, In connected to batt. 240 ohms from out to adj, and 510 ohms from adj to a 200 ohm pot, and the other side of the pot to ground.

The tap of the pot goes to the + input of an LM358. Connect the LM358 with a 2N3904 emitter follower on the output, and the emitter of the 2N3904 connects back to the - input of the LM358
LM358 VCC and Collector of 2N3904 connect to the LM317 output, about +5V.

Add a 100uF cap from LM317 ADJ to ground to lower the noise, and add a 22 ohm resistor from the emitter output to ground to preload the amp.

Sorry no CAD on this PC
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Old 20th August 2008, 03:56 AM   #9
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Personally, I would just try an LM723 (just the basic application circuit) if 5 mV regulation is acceptable.
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Old 20th August 2008, 10:05 AM   #10
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Quote:
Originally posted by leadbelly
Personally, I would just try an LM723 (just the basic application circuit) if 5 mV regulation is acceptable.
Hmmm ... just checked the data sheet .... the 723's opamp inputs are NPN; its input CMR won't extend to ground!

I'd just use cheap opamp that can handle 0V CMR (good ol'LM324 for example), together with an external reference (like a simple TL431) and divider/pot, plus whatever pass transistor is required (Darlington for more current).

This will go down to 0V without fussing with negative supplies etc., and has decent regulation. Make sure you tie up the unused amps (or use them for e.g. current limiting).
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