A question about a OP Circuit.

[Junker_eu]

can anybody tell me the function of below circuit?Thanks!

 

[MikeMl]

It is a useless circuit. As drawn, the output will sit saturated at ground because the inputs are both biased to ground because the Vss pin is also grounded.

 

[Junker_eu]

Hi,Mike,I don't think so.How the non-inverting input biased to ground.There is a Cap. C1.

And the circuit is not useless.It will amplify the DC input 11 times.But I dont know what is the using of the two Cap.

 

[MikeMl]

Then the bias for the non-inverting input must come from a DC component in the input signal.

See these sims, both for a DC sweep, and an AC frequency sweep. Get yourself LTSpice!!!

 

[Junker_eu]

Thanks,You are right Mike.But I want to know why the circuit can delay the pulse.(The output pulse is more width then input ).

 

[Junker_eu]

Thanks,You are right Mike.But I want to know why the circuit can delay the pulse.(The output pulse is more width then input ).

 

[MikeMl]

Thanks,You are right Mike.But I want to know why the circuit can delay the pulse.(The output pulse is more width then input ).

Draw the input pulse. DC level, amplitude, rise-time, fall-time, pulse-width, period?

 

[Junker_eu]

Draw the input pulse. DC level, amplitude, rise-time, fall-time, pulse-width, period?

Attatched picture is the result I simulated.THe yelow line is the input single pulse and the blue line is Output wave.I can not understand the result.

 

[MikeMl]

Ok, but what are the vertical/horizontal units on the scope trace?

 

[MrAl]

Hi,


The circuit also functions as a strange bandstop filter, where frequencies under around 105Hz get amplified, and frequencies above 1kHz get passed without too much attenuation, but frequencies within a certain bandwidth centered around 142Hz get cut quite a bit. So it's like a low pass filter and a bandstop filter. It may also be that it was made to work as a low pass filter with a very sharp cutoff.
That is of course assuming that the input signal has at least some dc bias voltage as well as the ac signal.

 

[Junker_eu]

Ok, but what are the vertical/horizontal units on the scope trace?

Foe the picture:

vertical unit:500ms per grid
Horizontal unit:2V per grid

 

[MikeMl]

Ok, I see what is going on. You are overdriving the opamp by input-ing a pulse that has no bias component (so the opamp rails to ground), and the pulse is so big that it rails on the top-end, too. In the sims, I show the difference between constraining the pulse so that it does not over-drive the opamp vs what you are doing to it. Note the ringing in the former which is suppressed by letting the opamp slam into its internal limits. The delay comes principally from the opamp recovering from being so badly overdriven.

If you goal is to build a pulse stretcher, there are much better ways of doing it.

Note that in my sim I'm using a better opamp than you (mine is true rail-to-rail IN and OUT), and it has a higher GBW.

 

[Junker_eu]

.

If you goal is to build a pulse stretcher, there are much better ways of doing it.

GBW.

Much better ways to build a pulse stretcher??Can you teach me some of them?Thanks!

 

[MikeMl]

What logic family? 5V supply?

 

[Junker_eu]

5V supply.

 

[MikeMl]

5V supply.

Delay at R1=100k, 300k, 500k, 700k and 900k.

 

[Junker_eu]

Delay at R1=100k, 300k, 500k, 700k and 900k.

You are so clever,Thanks.You create the circuit by yourself?!Great!

 

[Junker_eu]

Hi,Mike!Can you tell me the name of your circuit simulation tool? Thanks!

 

[MikeMl]

Hi,Mike!Can you tell me the name of your circuit simulation tool? Thanks!

LTSpice IV, free download here. User's Group on Yahoo.