Need help designing a filter(active)

[arunbhaskar]

I need help designing a opamp active low-pass filter.
I need the gain in the passband to be close to 1.
Passband cutoff frequency is 5Hz.
Transition band may go upto 50Hz.
I tried designing for above parameters using 2nd order sallen key filter. But that does not provide me unity gain for satisfactory frequency response. Can someone suggest a better circuit for the same job.

 

[keith1200rs]

Try Texas Instruments Filter Pro software. It is free and easy to use.

You should be able to get the response you require - what is actually wrong with the response you get? Can you show your circuit and results?

Keith

 

[LvW]

...................
Passband cutoff frequency is 5Hz.
Transition band may go upto 50Hz.

Sorry, but this is no filter specification. I suppose, you mean a low pass filter, but how could we know which order?
The second "information" is useless without mentioning the required damping at 50 Hz.

 

[arunbhaskar]

I'm sorry. I forgot to mention

Stopband attenuation is atleast 20dB.

 

[LvW]

For such a small attenuation of only 20 dB (one decade above the corner frequency) a first order (passive) low pass is sufficient.