Why 741 does not amlifies on period of low frequencies

[permute]

I agree. My guess is that the problem has been ill-posed, and that the actual circuit has a capacitor or transformer or any other AC-coupling device.

Such a case would have high-pass response, allowing higher frequencies to pass, while preventing lows.

Either that, or this "PhD" is human and put a typo in the question.

 

[a.dehqan]

I agree. My guess is that the problem has been ill-posed, and that the actual circuit has a capacitor or transformer or any other AC-coupling device.

Such a case would have high-pass response, allowing higher frequencies to pass, while preventing lows..

Thanks a lot for your attention ,
741 has a inner capacitor itself and that capacitor makes it to have frequency related results .
Anyway i(humble) will check my master question today .

Regards dehqan

 

[a.dehqan]

Hello ;

My master said again :

There is gain *10 at for example frequency=20 HZ But there is no *10 gain at F = 3 HZ .
Why ?

Regards

 

[FvM]

Why are you "changing" the frequencies with every post?

Anyway, the A=-10 gain is constant from frequency 0 (DC) up to about 150 kHz (according to 741 typical bandwidth),
so it's -10 for 3 Hz and 20 Hz as well.

 

[LvW]

Hello ;

My master said again :

There is gain *10 at for example frequency=20 HZ But there is no *10 gain at F = 3 HZ .
Why ?

Regards

Why? How can we know why your master (master of what?) did tell you such surprising things? Perhaps he was joking.
You shouldn't ask us. Better ask him.

 

[a.dehqan]

Why are you "changing" the frequencies with every post?

Anyway, the A=-10 gain is constant from frequency 0 (DC) up to about 150 kHz (according to 741 typical bandwidth),
so it's -10 for 3 Hz and 20 Hz as well.

Hello ;
Thanks a lot
Because these frequencies are example but we know it s a period in low frequencies .

You should see 741 behavior in Reality not in theory .
be sure question is ok just see it's behavior in Reality

He has PHD and is Group Manager of electronic department

Regards dehqan

 

[LvW]

Silly question: Is there perhaps an input capacitor in addition to the shown circuit ? (see also the reply from permute, yesterday).

 

[FvM]

but we know it s a period in low frequencies

You know what?

You should see 741 behavior in Reality not in theory.

I see it since decades, but I wonder, if you ever did?

 

[aomidee]

Because 741 has capacitor effect in its structure. So frequency should be higher than capacitors frequency

 

[FvM]

Because 741 has capacitor effect in its structure. So frequency should be higher than capacitors frequency.

Sorry, I don't know what you mean. The only relevant "capacitor effect" is the internal (miller) frequency compensation which causes a first order low-pass characteristic of open loop gain and a respective limitation of closed loop bandwidth. There are also additional poles of open loop gain that get effective in the MHz region.

The said behaviour is basically common to all OPs compensated for unity gain. I'm not aware of a specific frequency characteristic of LM741.

See an internal 741 schematic for illustration.

 

[heri.aza]

there is no capacitor in 741 internal diagram... may be you need to ask your master (again) about this...

 

[keith1200rs]

there is no capacitor in 741 internal diagram... may be you need to ask your master (again) about this...

I think you will find there is a capacitor - C1. FvM has already explained its effect.

Keith.

 

[LvW]

Because 741 has capacitor effect in its structure. So frequency should be higher than capacitors frequency

Is your statement based on (a) knowledge or (b) assumption/assessment ?
(...has a capacitor effect in its structure...??? What is a "capacitors frequency"?)

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