THS3217EVM: THS3217 Gain simulation vs real circuit

Hi Justin,

It looks like you are inputting the signal into the non-inverting input of the power amplifier which would give a gain of 2.5V/V or around 8dB. Assuming you are using the same Rf and Rg, they should be very close to each other. I am curious if you are calibrating the instrument prior to running the sweep. Ideally we should see a flat response from 30kHz up until the device starts to loose bandwidth. I am not sure if this is normal in your instrument but I am wondering if it is due to this?

Best Regards,

Ignacio

Hi Ignacio

Thank you for getting back to me. We did calibrate our network analyzer properly with Response Calibration. We verified our network analyzer with a thru cal check and get the same 6dB result.

thru cal check: https://drive.google.com/file/d/1JItCnYyASNQIiTSW9PX4EKkC-L_SnHji/view?usp=sharin

Hi Justin,

Unfortunately, we cannot see google docs through our network so if there is an image you are sharing it might be easier to directly attach an image. However, I am confused why you are seeing this value. If you look at Figure 27 in the datasheet, we are testing the power amplifier and do get 8dB. If you are using the same resistor there is no reason you should be getting 6dB unless something in the setup is not being accounted for.

Best Regards,

Ignacio

We ordered a brand-new THS3217EVM to verify, and we are still getting the same results.

Additionally, we compared the J6 and J8 (Still OPS only) and we got an excess of -50dB. This should be 0dB.

Hi Justin,

Can you confirm what pin 10 and 4 are in your configuration. Just to confirm, for the 6dB result you are setting the input signal to J8 (pin 9 of the device). You are then measuring at J7 (pin 11 of the device) and in this test you do not change R34 and R33 correct? Can you confirm your supplies? Is it +/-7.5V?

Best Regards,

Ignacio

Yes, those are all correct. We did not change any resistor values, and our supply is +-7.5.

Additionally, we tested the full stage of the board. J1 and J2 as our input differential signal and J7 as our output. We still found that gain is closer to 6dB then the 8dB seen in the datasheet. It feels like we have tried every possibility. Is there any way to setup a call to further get support on this siutation

Hi Justin,

Let me get the measurement setup in our lab to see if I get the same result as you. I will likely be the easiest way to understand what might be happening. I will follow up with you as soon as I get the test completed.

Best Regards,

Ignacio

Hi Justin,

I went ahead and used a new THS3217EVM with the same supplies and got 8dB on the flat region of the frequency response. It is around 2dB, which is due to the 6dB drop from the internal termination of the instrument and R34 on the EVM.

Best Regards,

Ignacio