What does this op amp do?

[brucester]

Last beginner question from me for a while.

I made this circuit on a sim:



http://www.falstad.com/circuit/#%24+...625E-5+2+-1%0A

The bottom left and middle scopes are the input signals to the right most opamp. The bottom right scope is the output.

My question is, what does that curve mean?

I mean, what did the opamp do to the input signals to come out with that?

I am not looking for a lengthy explanation i will will go off and google for more detail but if someone could tell me the purpose of that opamp and what its out put is it would be appreciated

Thanks

[brucester]

Ok, after some more google research i am slowly getting the picture.

Ok, so the opamp has no feedback, which makes it a comparator.

The signal is fed through the negative input which makes it an inverting comparator which will explain the opposite curve.

Now, what is it comparing the pre amped flyback decay to?

And comparators produce square waves, as this one does as soon as you switch the coil on and off, but if left on or off, it swings to just above the middle.

Why would a comparator, which is essentially a digital switch, produce an analog curve?

Am i on the right track?? :P

This is the circuit i am trying to figure out, the lovely russian pirate:



I have figured out the pulse width and frequency, i understand the preamp gain, but after preamp, i have no idea what this thing does.

It seems to control the pitch of the speaker with the curve of the comparator opamp.

Any more info would be good

[mikebg]

Brucester, Your activity in the forum is guided by the principle:
When a new year starts, start a new thread.
Last year you started a thread with the same problem and got enough answers.
http://www.geotech1.com/forums/showt...ector-possible

[brucester]

??

That thread was to find the simplest PI MD possible. This thread is about how it works. Fair enough i could have posted this in there, but where is the fun in that? :P

[Qiaozhi]

Ok, after some more google research i am slowly getting the picture.

Ok, so the opamp has no feedback, which makes it a comparator.

The signal is fed through the negative input which makes it an inverting comparator which will explain the opposite curve.

Now, what is it comparing the pre amped flyback decay to?

And comparators produce square waves, as this one does as soon as you switch the coil on and off, but if left on or off, it swings to just above the middle.

Why would a comparator, which is essentially a digital switch, produce an analog curve?

Am i on the right track?? :P

This is the circuit i am trying to figure out, the lovely russian pirate:



I have figured out the pulse width and frequency, i understand the preamp gain, but after preamp, i have no idea what this thing does.

It seems to control the pitch of the speaker with the curve of the comparator opamp.

Any more info would be good

The russian pirate circuit is using an opamp as a comparator, so it does not have the same fast slew-rate. Hence, the output swing has an "analog" look to it.

[Ferric Toes]

??

That thread was to find the simplest PI MD possible. This thread is about how it works. Fair enough i could have posted this in there, but where is the fun in that? :P

I was not aware that you had all this information last year, otherwise I would not have wasted an hour drawing up the schematic I posted today in this years thread. All the information you need is under PI Principles in the book.

Eric.

[Carl-NC]

First, your sim circuit appears to have an error, check C7. The comparator compares the preamp output to a slowed version of itself. This makes it a motion detector.

[brucester]

I was not aware that you had all this information last year

What info? The info i got was the location of the schematic, nothing about the actual circuit and what it does. It comes from a russian forum and i dont speak russian and the google translate is extremely hard to follow hence the question.

Last year you started a thread with the same problem

So confused :P Again, that thread was a mere request for a simple circuit. This question is about the simple circuit that thread found. It's like asking where the chess room is then finding the chess room then asking how to play chess only to have people reply that you asked where the chess room was moments ago so no more help for you. Ok, bad analogy but u get the idea :P or maybe u dont....

The russian pirate circuit is using an opamp as a comparator, so it does not have the same fast slew-rate. Hence, the output swing has an "analog" look to it.

Ahh, i see. Thank you.

First, your sim circuit appears to have an error, check C7. The comparator compares the preamp output to a slowed version of itself. This makes it a motion detector.

Thanks Carl. I'll check it out and come back :P