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LM723 IC with Mos-Fets output???

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The-dude

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Hi there everybody.

I have just registered.

I would like some help of you if you can give some.

Is it possible to make a PSU with the LM723 IC about 20A BUT NOT with output transistors like 2N3055 or equiv. I want it with Mos-Fets output so as to have low drop voltage (in-out) and good efficiency.I want it for 3-12Volts.

Is it possible?

Thanks in advance.

The-dude.
 
Here is the APP Note and Datasheet
 

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  • lm723_national_111.pdf
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I have used it with N-channel as a low dropout regulator. Only problem is the gate has to be about 5 volts higher than the source. I used a voltage pump to power the 723 and used about 180 ohms from the 723 output to the gate of the mosfet. In my case it was a low dropout regulator for 12V.
The in/ out differential was about .3 volts.
I think if you used a P-channel and connected the source to the regulator input, and had the drain as the output, you would not need to use a voltage pump.
 
I have built a supply with the mosfets but I used two LM723 and a small extra (2.5VA) transformer for supplying the regulators and it worked fine.

Ante :roll:
 
ante said:
I have built a supply with the mosfets but I used two LM723 and a small extra (2.5VA) transformer for supplying the regulators and it worked fine.

Ante :roll:

and how did you do it?Thanks. :)
 
Hi Dude,

I have a hand drawn circuit (15year old), I will straiten it out and post it for you.

Ante :roll:
 
OK Dude,

Here it is and I hope there are no mistakes. With the values given it is 0 – 25 Volts and 4A.

Ante :roll:
 

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  • 723_psu.zip
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Thanks Exo,

Well let’s say I didn’t draw it on a Monday :D . You haven’t seen my doodle, :oops: and I promised to straiten it out so I got some help from Eagle.

Ante :roll:
 
The-dude said:
I want it with Mos-Fets output so as to have low drop voltage (in-out) and good efficiency.I want it for 3-12Volts.

I don't really see the reasoning behind wanting FET's rather than bipolar transistors? - the really neat design by 'ante' even has to have a second mains transformer to overcome the limitations of the FET's. Bipolar outputs would only require the base to be 0.7V higher than the emitter, the FET solution requires far more.

Also, why is it 'more efficient'?, admittedly the bipolar solution requires highish base currents - but this is only a small percentage of the output current, and not terribly significant.
 
Nigel,

You are quite right; bipolars is easier to handle in a circuit like this. The extra transformer is only a small cheap one but anyway I still agree. There are many different solutions but the “Dude” wanted one with the 723 so there it is. If omitting the 723 I have better suggestions.

Ante :roll:
 
723

if you do not use the 723 what is better
i have being looking most people only refer to the 723
i would like to know

mike
 
Hi Eric,

Yes, and that's quite a complex circuit using two 723's just to build
a linear regulator.
 
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