OPA1664: I need a delay of 1.25ms till upper limit of 400Hz

Hi Goldy,

Goldy Rathore said:

I need a delay of 1.25ms till upper limit of 400Hz. Can you please tell below?

You may modify the all-pass filter delay circuit (scale the circuit linearly). Here is how.

a. 1.25msec/155.28usec = 8.05

b. multiply all 8 resistors' value by a factor of 8.05 respectively. 

c. This will shift the pole from 3..814kHz to 472Hz --> this should give you the similar time delay characteristics (within 400Hz the delay error stays <10%)

d. Change the op amp with OPA1664 (BW = 22Mhz)

e. Use NP0/C0G or polyprolyene capacitors (2%), and use 0.1% resistors, if you want to be more precise (1% is acceptable depending on your timing requirements).  

Goldy Rathore said:

3) How many op-amps are needed?

The 3-op amp all-pass filter delay should work. If you want to be more precise, then you may try to add another OPA1664 using same technique. 

Please let me know if you have other questions. 

Best,

Raymond

Thanks Raymond,

I am good to go.

Very good support from TI, I appreciate

Thanks and Warm Regards,

Goldy