# How to Stabilize the Output Voltage Using a OP AMP Comparator Circuit and Draw Current(1A) from it?

#### Debraj Das 3

Joined Mar 11, 2019
5
I wanted to design a power supply which can supply about 1A at (+-12v) to (+-15v)so I chose to use the regulator IC like 7812 and 7912 and now I have heard that we can actually use a comparator circuit to stabilize this output voltage further but I don't know how to do it.Can Anyone tell me how to get more stabilization using comparator and actually how much current can I draw from this circuit without dropping the output voltage and it will be better if someone can tell me to how to draw about 1A current from this comparator circuit without dropping the voltage?
Here is the basic structure of my Power Supply Circuit

A 24-0-24 2A transformer Bridge RectifierC FilterRegulator IC(7812 & 7912)Comparator CircuitStabilized (+-12v)to(+-15v) 1A output

#### crutschow

Joined Mar 14, 2008
34,689
I have heard that we can actually use a comparator circuit to stabilize this output voltage
And where did you hear that?

You seem to be confusing two different power supply techniques, linear and switching.
The linear approach uses a linear regulator, such as the 7812 or 7813, to provide a regulated DC voltage.
The switching approach uses switching devices, such as a comparator, in conjunction with other switching devices, to generate a DC output voltage.

I don't see any obvious way to use a comparator to help regulate the output of a linear regulator.
(And I don't see why you would want to since those linear regulators regulate the output voltage very well.)
I suggest you go to wherever you "heard" that to find out what they are talking about.

#### DickCappels

Joined Aug 21, 2008
10,230
Perhaps you are looking for something like this? Tracking voltage regulator.

If you look around you might be able to find and LM317 serving as the output stage for an op-amp stabilized opamp.

By the way, comparators are different fromopamps with the same schematic diagram.

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#### ericgibbs

Joined Jan 29, 2010
19,000
hi Dick,
E

#### DickCappels

Joined Aug 21, 2008
10,230
Thank you Eric. I saw that too but it is ok now. I think it was one of thse temporary errors.

#### AlbertHall

Joined Jun 4, 2014
12,385
Nope, still doesn't work here.

Joined Mar 10, 2018
4,057

#### Debraj Das 3

Joined Mar 11, 2019
5
And where did you hear that?

You seem to be confusing two different power supply techniques, linear and switching.
The linear approach uses a linear regulator, such as the 7812 or 7813, to provide a regulated DC voltage.
The switching approach uses switching devices, such as a comparator, in conjunction with other switching devices, to generate a DC output voltage.

I don't see any obvious way to use a comparator to help regulate the output of a linear regulator.
(And I don't see why you would want to since those linear regulators regulate the output voltage very well.)
I suggest you go to wherever you "heard" that to find out what they are talking about.

#### Debraj Das 3

Joined Mar 11, 2019
5
Sorry Sir,but I too am confused how to do that that's why I have came here and I too am not seeing any way to use comparator as a voltage regulator...and I have heard this from one of my ex-teacher who have retired now so there is no way to contact him that's why I came to here and posted this thread...can u please explain me what is this switching approach u talked about actually I am just started learning electronics that's why I don't have much knowledge...

#### sghioto

Joined Dec 31, 2017
5,420
I saw that too but it is ok now.
The spec sheet for the LM78 series shows using a comparator circuit as a tracking voltage regulator.
SG

#### ericgibbs

Joined Jan 29, 2010
19,000
hi DD3,
E

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#### DickCappels

Joined Aug 21, 2008
10,230
Another. These days there are better ways to make a 1 A adjustable power supply.

A better way:

#### crutschow

Joined Mar 14, 2008
34,689
View attachment 172075
That reference states it discusses both linear and switching regulators, but I only see a discussion of linear.

#### crutschow

Joined Mar 14, 2008
34,689
The spec sheet for the LM78 series shows using a comparator circuit as a tracking voltage regulator.
I see a tracking circuit using an op amp but not a comparator (below).

#### ericgibbs

Joined Jan 29, 2010
19,000
That reference states it discusses both linear and switching regulators, but I only see a discussion of linear.
hi,
I noticed that too, anyway I considered it would easier for the TS to get savvy on Linear before reading up on SMPS.

E
This PDF should give him an insight into SMPS

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#### sghioto

Joined Dec 31, 2017
5,420
I see a tracking circuit using an op amp but not a comparator
I said a comparator circuit.
SG

#### Alec_t

Joined Sep 17, 2013
14,379
Here's a primitive regulator using a comparator:

#### crutschow

Joined Mar 14, 2008
34,689
I said a comparator circuit.
SG
So you did.
So where did you see this comparator circuit?
The 741 is an op amp, not a comparator.

#### Debraj Das 3

Joined Mar 11, 2019
5
So you did.
So where did you see this comparator circuit?
The 741 is an op amp, not a comparator.
Sir,as far my knowledge goes,any op amp can be used as a basic comparator when using in open loop configuration

#### crutschow

Joined Mar 14, 2008
34,689
Sir,as far my knowledge goes,any op amp can be used as a basic comparator when using in open loop configuration
True.
But in the circuit I posted the op amp is closed-loop, not open.
Used as a comparator for JHC.
We seem to be going in circles.
What's JHC?