Is this circuit safe for a J-fet Op-amp ?

[pedroteck]

When comparator kepp turning on n off at fast rate.i dont look at ur circuit,just questioning possibility,you should check it with ur scope.

There is noswitcher in this circuit. Qnd its current controle design for a led.

[Alex30]

Seriously guys the smart alec comments don't help anyone. This thread should belong in the beginners section but being told your question is stupid can be really off putting for newbies. Not all of us have a university degree in electrical engineering or any engineering experience at all you know.

OP, what exactly is it you want to check out? Yes a comparator is something you can make with an opamp but as others have said, not all opamps should be used for this because they will oscillate. If you want to learn about opamps try circuits specifically for opamp applications, such as differential amplifiers or negative feedback gain etc. If you have a scope and a cheap function gen (even a couple of dollars on ebay can get you a cheap function generator) try hooking up the opamp to provide gain on various signals and have a go at using the opamp as an integrator etc. As you learn have a go at understanding the calculations and opamp properties such as output swing.

Most opamps don't like it if your input voltage is close or higher than the positive input rail, also do not make your input any less than the negative rail. For example if you have the negative rail at ground, do not provide the opamp with -2V etc. Some are better than others, but all this stuff should be in the datasheet if you hunt for it.

Have fun!

[dannyf]

but how could this led be blinking ?

By adjusting the pot, you can control the circuit through the led, turning it on and off -> ie. blinking.

What OP had created is a voltage-controlled current source.

[paulie]

Seriously guys the smart alec comments don't help anyone. This thread should belong in the beginners section but being told your question is stupid can be really off putting for newbies.

Then IMO they are in the wrong hobby and no business on a forum.

We will have to agree to disagree on this. My observations indicate tough love usually proves more effective than coddling. In fact IIRC the communists during Maos reign demonstrated gentle coaxing with electro-reinforcement most effective of all.

[kg4arn]

"LOL. Good one. Except by definition there is no such thing as FET 741."

Actually, I have some of these. From the datasheet:  "The LF13741 is a 741 with BI-FET input followers..."

[Alex30]

In fact IIRC the communists during Maos reign demonstrated gentle coaxing with electro-reinforcement most effective of all.

Brilliant hahaha. Can't argue with hard evidence haha

[pedroteck]

OP, what exactly is it you want to check out?
Have fun!

All i wanted to check is weather the opamps i have are working or not .

[rob77]

btw.. what's wrong with 741 ?  a 2+ decades old metal canned version of 741 is very nice decorative item !

[wiss]

OP, what exactly is it you want to check out?
Have fun!

All i wanted to check is weather the opamps i have are working or not .

apply +- supply (10 - 15 V or so, depending), 0 on +in, -in to out.
measure output voltage, should be within Vos of +in.