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THS3217EVM: Using THS3217 as bias tee to add DC to a signal

Kelly
Intellectual 350 points
Part Number: THS3217EVM
Other Parts Discussed in Thread: THS3217

Hi there,

Can I use THS3217 as a bias tee to add DC to a single-ended AWG output (e.g Vin+ for signal and Vin- for DC)? Our application prevents us from using conventional bias tee which has lower cutoff frequency higher than we want (we need the lower cutoff below 1kHz). I've tried the approach I mentioned and I can shift the signal level but the gain is pretty low after D2S (around -4dB). Although I can use OPS stage the frequency response of the EVM becomes poor when OPS is enabled.

Best wishes,

Kelly

  • 0
    Guru 48395 points

    Hello Kelly, 

    It would be helpful to see schematics or even better TINA files.

    Keep in mind the THS3217 has an onboard buffer intended to be used as a DC level shift feature - The D2S prefers to operate with a differential input, but you can level shift its output using that buffer connected into that Vref pin. The Buffer was designed to be very low output impedance boardband so you get that DC level shift function but do not mess up the D2S operation. 

  • 0 in reply to Michael Steffes
    Intellectual 350 points

    Hi Michael,

    Thank you for your reply. I’ll give the TINA model a try later. I understand that THS3217 is designed for differential inputs, but our AWG does not have differential outputs. The reason I chose THS3217 is its higher bandwidth. Do you have any other EVMs which can do the level shifting job but also have at least 300MHz bandwidth and accept single ended input? Also for 3217 would it be possible that I use one input port and ground the other port?

    Kelly

  • 0 in reply to Kelly
    Guru 48395 points

    Yea, I think it will work - the THS3217 was intended to be the Complementary DAC to single ended conversion stage in an AWG, so this is some chance there is already one back behind your AWG output. It would be easy to sim.