Hi colleague,
Our customer encounter below issue:
After the signal output by the DAC passes through the THS3001, the total harmonic distortion of the 1MHz signal is -68dB. From the data sheet, the THD is less than -96dB.
So is there any problem with the op-amp? Thank you.
The op-amp circuit is as follows: The front stage of the op-amp is the DAC current output; the rear stage is the filter.
Morning Mr. Su,
Cannot answer this question without the full load model and output swing.
I would say you should reduce those input 1kohm to the IN+ nodes nodes to 20ohms. They probably put them there thinking they were getting bias current cancellation, not possible on a CFA like the THS3001.
Also, you may have stability issues due to the relay capacitance on the lower amp inverting node. Would need a model for that.
This I think are the plots you are referring to - note these are only 2Vpp out
