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to amplify signal- must not to non linear!

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RSharifi

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Dear All,
I simulated the bellow circuit and I satisfied with the design.

https://obrazki.elektroda.pl/9939415700_1440399796.png

But in the experimentation I have a non linear problem.
As increasing the amplitude at the input, the ratio of amplification isn't constant!
What can I solve the problem?

Regards,
Rasool
 

what is your input spec for VG2?
 

Dc: 0-100 V

- - - Updated - - -

this is a dc voltage in the range of 0-100 V
 

Hi,

it is a 2nd order sallen key low pass filter.

If your connections are right, then it should have an input range of about +/- 200V.

Is your R7 able to dissipate 30W of power?

Connect GND_Ref (C1, R3) for the OPAMP directely with extra wire to R8.
Connect R2 directely with extra wire to R8.

Klaus
 

The R7 is load which its current sensed with the R8.
I have problem in practice;No in simulations!

Rasool,
 

please suppose,
in=33 V ==> out=1.4 V

in=66 V ==> out=2.6 V ! which should be 2.8 V
 

Hi,

What is R7? Is it a true resistor?
Or is it a copper wire, a heating device, a light bulb, or something else? If so, then this is the problem. It is non linear.


Klaus
 

Yes,
It is good point.
I should to test it ( in next days ).

regards,
Rasool
 

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