THS3001EVM: measuring frequency response over 50MHz

TkMk

Part Number: THS3001EVM
Other Parts Discussed in Thread: THS3001Hello, I just tried to measure frequency response using ordinary passive voltage probes(10Mohm, 8.0pF). I found that over 50MHz, the result is not consistent with Figure1-5 at User's Guide(slou021a.pdf) . My question is how to measure frequency response over 50MHz. Using the active voltage probes? They stil have some stray capacitance. How far they likely work on THS3001EVM? Using the 50ohm coaxial cables and Frequency Response Analyzer? In this case, where to put Rload150ohm? Regards, Tak

over 5 years ago

0 Jacob Freet over 5 years ago

TI__Expert 7875 points

Hi Tak,

You will likely have measurement issues at high frequencies unless you can find a very low capacitance probe. I would suggest using the standard SMA connectors that are on the EVM and connecting them to a network analyzer to measure the frequency response. The EVM board is already set up by default with 50 ohm input and output matching so that you can easily connect to test equipment.

Regards,

0 TkMk over 5 years ago in reply to Jacob Freet

Prodigy 140 points

Dear Jacob,

Thanks for your suggestion.
I am not sure how to put Rload 150ohm while keeping 50ohm matching at the SMA output connector.
Is there an advice on this?

Regards,
Tak

0 kai klaas69 over 5 years ago in reply to TkMk

Guru 140200 points

Hi Tak,

why 150R? It is 50R. Just connect a 50R cable to the output of EVM and connect the other side of cable to a 50R input of test equipment.

Kai

0 TkMk over 5 years ago in reply to kai klaas69

Prodigy 140 points

Hi Kai,

The IC output current is limited, so, to get large voltage output, Rload must be large ohm.
I saw THS3001 datasheet toppage figure and THS3001EVM User's Guide figure1-5.
This IC will work with Rload=150ohm and I would like to measure it.

Tak

0 kai klaas69 over 5 years ago in reply to TkMk

Guru 140200 points

Kai

0 TkMk over 5 years ago in reply to kai klaas69

Prodigy 140 points

Hi Kai,

Thanks for the resistor circuit.
IOP1 see 150ohm and cable see 50ohm.
I will try measurement with this.

Tak

0 kai klaas69 over 5 years ago in reply to TkMk

Guru 140200 points

:-)

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THS3001EVM: measuring frequency response over 50MHz