OPT8241-CDK-EVM: Modulation frequency measurement using an oscilloscope and photon detector

sean chen97

Prodigy 40 points

Part Number: OPT8241-CDK-EVM

Hello,

on CDK, i measure the waveform of trig_G based on default profile, it shows about 60MHz.

and use photo-detection sensor to measure the illumination. but I can't see the higher-freq modulation.

Does anyone have the same question? and I'd checked the PD bandwidth enough to measure on our module, its 72MHz.

the ch4_green is trig_g, then chM_red is PD output.

over 7 years ago

0 Subhash Chandra Sadhu over 7 years ago

TI__Expert 3800 points

400mV is a very high voltage for a typical high speed Silicon PIN photo-diode. It is unlikely that you are getting so much voltage from the oscilloscope in 50 Ohm mode.
I think your oscilloscope is in 10kOhm mode and you are seeing reduced bandwidth, higher voltage. Can you change the oscilloscope settings to reduce the input impedance to 50Ohm? You would have to considerably change the vertical (Voltage) scale to be able to see the signal.

Regards,
Subhash

0 sean chen97 over 7 years ago in reply to Subhash Chandra Sadhu

Prodigy 40 points

Hi Subhash,

thanks for your answer.
it works now.

brs, Sean

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OPT8241-CDK-EVM: Modulation frequency measurement using an oscilloscope and photon detector