Hi,

I have designed the strain measurement circuit with instrumentation amplifier and RC low pass filter.
Gain =10, Vsin = 2 v, input Freq = 2 kHz, cut off frequency fc = 15.9 kHz. The circuit is working efficiently until the frequency of the input is varied to 6 kHz but beyond these value the output is unpredictable that is amplitude is decreasing.

Please find the attachment of the circuit screen shot and Lt Spice model is attached.

Thanks and Regards,
Richi Nixon V

 

It says opamp2 undefined. When I tried it with LT1007 the -3dB bandwidth was roughly 6kHz. AC analysis is much better for analysing bandwidth than transient.

 

Yes, even with LM741 I am able to get 6kHz and I tried with AC analysis too.

Thank you

 

When you delete the second stage you get that ~15kHz corner. However when you stack two stages together without any buffer they infulence each other and the corner shifts, in this case lower.

 

Indeed it's happening the way suggested..
Any work around! What if incase use of Bessel filter

 

You can use whatever filter you want, but you need to calculate it properly. If you change the values to get the required corner everything should be fine with the simple one.

 

Ok...will look into it, many thanks again.