How to activate the APD' input gate (SPCM-AQRH-15, Perkin Elmer) by TTL pulse generated by PCIe 6351?

[palm79]

Hi everyone, I'm newbie in electronic stuff. In my experiment  I'm using the APD photodiode from Peikin Helmer (SPCM-AQRH-15) to count # of photon (fluorescences). I want to gate the APD by applying on the APD' input gate a TTL pulse (which generated by Labview via PCIe 6351). This pulse, although clearly displayed in an osciloscope (Textronix) with 10µs pulse width but it does act on the APD (the APD responses nothing to this pulse). I read SPCM-AQR series' datasheet, which says that "The GATE input (BNC connector) impedance is 50 ohms and internally connected to the +5 volt supply through a50 Ω pull-up resistor (standard module versions). It canbe driven by standard TTL level signals. The gatedrive must becapable of sinking 100 mA to gate the module off (5V/50 Ω). Operation: TTL high – module counts, TTL low–counting disabled".

I don't know exactly the "current sink" means and how to get it in a BNC connector.
Could anyone instruct me how to gate the APD by a TTL pulse generating by PCIe 6351 board? Any help will be appreciated.
Thanks in advance.

[JÞB]

Since the 6351 can sink or source a maximum of 24mA per line you are going to need a driver inbetween.  Some darlington pair would work just fine

[palm-ensc]

Dear Jeff,

Thank you for your suggestion and the link you provided. In fact, is it possible to make the device (a circuit actually) which acts the same as the darlington pair does? 

Do you have the sketch for that circuitry?

best regards,

Trang,

[Dennis_Knutson]

There is a schematic in that pdf file. Did you read it? If you are new to electronics, you should just buy the ic. It's cheap.

[palm-ensc]

Yes, I'm new to electronics so the best way is to by that IC. Thank you very much.