Hello,

I only have dual supply op-amps that require a minimum supply voltage of +/- 10V, and I want to use the comparator configuration. The comparator will either output -10V or +10V, but I want to make 0V and 5V, respectively, from this. What's a simply way to do this?

 

FET, a couple of resistors.
This (
1HN04CH-TL-W)
http://www.digikey.com/products/en/...t=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25 should work.

Vgs is within range. It's a logic FET, You'll need a pull-up resistor to +5. Drain to ground. And usually a resistor to have a place for the gate leakage to go, but your driving it, so that's not needed. The series gate resistor is included too.

 

a minimum supply voltage of +/- 10V

What is the ic needs so much high minimum power?
Many comparators has open collector(bjt) or open drain(N mosfet), the output is in a floating status when output is high and can be supply with single power, so if your comparator can match above described then it can be supply single +5V,0V, and the output needs to using a resistor as 4.7K or 10K to pull high, so when the output is high has a high level as +5V to output.

 

FET, a couple of resistors.
This (
1HN04CH-TL-W)
http://www.digikey.com/products/en/discrete-semiconductor-products/transistors-fets-mosfets-single/278?k=&pkeyword=&pv608=2303&FV=ffe83f21,98004d1,98008ff,1f140000,1f280001,1f28000e,ffe00116,1c0002&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25 should work.

Vgs is within range. It's a logic FET, You'll need a pull-up resistor to +5. Drain to ground. And usually a resistor to have a place for the gate leakage to go, but your driving it, so that's not needed. The series gate resistor is included too.

Thanks, do you mean source to ground though?

 

What is the ic needs so much high minimum power?

Im using lm741. Think I misunderstood the data sheet. It says recommended Supply voltage +/-10V, but i guess that actually means i can supply it with V+ to 10 and V- to 0?

 

Im using lm741. Think I misunderstood the data sheet. It says recommended Supply voltage +/-10V, but i guess that actually means i can supply it with V+ to 10 and V- to 0?

The LM741 can be supply ±18V or higher, so how high do you need that is depend on what kind of application are you using.

And next times when you using op amp as comparator then you have to mention it, otherwise we will thought that you are using the real comparator, I also used the LM324(4 op amp inside) as comparator.

When you using this old op amp, you should know that it has a higher low level output as 1.4V, but the modern IC almost as 0.2V.

So now please tell us what do you trying to do for the op amp?
(Input Voltage/Output Voltage and function, purpose)

 

Im using lm741. Think I misunderstood the data sheet. It says recommended Supply voltage +/-10V, but i guess that actually means i can supply it with V+ to 10 and V- to 0?

You also didn't read the data sheet for the input range.

You can see that the input will only go to within about 2-3V of the supply rails (the value shown is for supply voltages of ±15V.
Thus with 10V for V+ and 0V for V-, the input voltage range is only between 2v to 3V (or less).

If you need a comparator, then use a comparator such as the LM339/393 and operate it from V+ and ground (0v).
Its input goes to 0V
The output is open collector and you just need an output resistor (10kΩ or so) going to +5V for a 0-5V output.

 

Thanks, do you mean source to ground though?

I din;t say that.

+5====resistor P===Logic tap(0-5)====source=Drain=====Ground

Logic input==Gate==RESISTOR A==Ground


Resistor P is the pull-up.
Resistor A bleeds the gate leakage current to ground. It's not needed if your driving it push/pull which you are.

There is an internal gate series resistor - so your good to go there.
There is internal voltage protections for the gate, so your good to go there.

 

Hello,

I only have dual supply op-amps that require a minimum supply voltage of +/- 10V, and I want to use the comparator configuration. The comparator will either output -10V or +10V, but I want to make 0V and 5V, respectively, from this. What's a simply way to do this?

Many comparators are open collector output with external pull up resistor, so I'd start by lifting the op-amps and fitting actual comparators - then its relatively simple to put a current limiting resistor in series with the output so the transistor ratings aren't exceeded and simply clamp the free end of that resistor with Zeners and/or diodes to whatever voltage swing you need.

Its not impossible if you leave the op-amp in place, but there's a few extra equations to keep an eye on, and comparators work much better as comparators than op-amps do.

 

You also didn't read the data sheet for the input range.
View attachment 122054
You can see that the input will only go to within about 2-3V of the supply rails (the value shown is for supply voltages of ±15V.
Thus with 10V for V+ and 0V for V-, the input voltage range is only between 2v to 3V (or less).

If you need a comparator, then use a comparator such as the LM339/393 and operate it from V+ and ground (0v).
Its input goes to 0V
The output is open collector and you just need an output resistor (10kΩ or so) going to +5V for a 0-5V output.

http://www.ti.com/lit/ds/symlink/lm741.pdf
Na, I can't be bothered to make numbers up.

I will try to obtain an actual comparator.

 

I din;t say that.

+5====resistor P===Logic tap(0-5)====source=Drain=====Ground

Logic input==Gate==RESISTOR A==Ground


Resistor P is the pull-up.
Resistor A bleeds the gate leakage current to ground. It's not needed if your driving it push/pull which you are.

There is an internal gate series resistor - so your good to go there.
There is internal voltage protections for the gate, so your good to go there.

Oh, I see. Thanks.

 

Na, I can't be bothered to make numbers up.

Sorry, I don't follow what you are saying.

 

Hello,

I only have dual supply op-amps that require a minimum supply voltage of +/- 10V, and I want to use the comparator configuration. The comparator will either output -10V or +10V, but I want to make 0V and 5V, respectively, from this. What's a simply way to do this?

LM311 or dual LM319