APD design ideas?

[pavjayt]

APD design Suggestions

Hello,

I am planning to design a new photo detector based on an APD. We currently salvaged a very old APD off of a commercial system which seems to be hand made. It has CLC300A Comlinear wide band amplifier and a RCA C30950E APD. Attached is a picture of it.

The specs of the APD and Comlinear looks very good, but when we connect it and have a laser shooting the diode, the response is not as expected. I am also not clear why it has a 15KHz clock input on one of the input connectors.

Apart from this if you have any ideas on designing a good APD and wouldnt mind sharing it, that would be great. I know I have to define my specs before designing one, but just want to know if anyone has experience in designing these things.

Also I was not able to find any datasheet on AIE part. It looks like its a DC-DC converter since the bias voltage of the APD is ~600V, but again this is like 30 year old one.

thanks

 

[Brevor]

What does APD mean ?

 

[pavjayt]

APD - Avalanche Photo Diode

 

[pavjayt]

Hello,

Could someone give me some leads/suggestions on where I can make any tweaks or upgrades to the attached design to be more reliable and robust with as much low noise as possible after the amplifiers?

APD - C30902-DTC
Resistor R2 - OHMITE TA205PA2R00J

Not sure about the value of C5 in the current design as I can't measure it, but there is a design example on OPA847 datasheet in a similar scenario using with a photodiode.

Importantly I would like to beef up the temperature control section to control the APD temperatures as described in section '- TC and - DTC TE-Cooled Versions ' on page4 of the Diode's datasheet.

thanks

 

[pavjayt]

Anyone with any ideas on improving the circuit??

Or can anyone suggest me some ideas on how to implement TE cooler feedback loop and temperature compensation as mentioned in the datasheet above for the diode??

"The thermistor located inside the unit can be used to monitor the APD temperature and can be used to implement a TE cooler feedback loop to keep the APD at a constant temperature and to implement a temperature compensation on the APD bias voltage. "

My bias voltage supply goes from 0-225V (typical Vbr for the diode).

thanks

 

[kubeek]

Not sure about the heater as I didn´t read those datasheets, but the gain stage looks wrong to me. Especially the floating + input of U2, it is not a very good practice to leave a high impedance input floating, no matter that it has a cap to ground.

anyway, the TE cooler will work like any other cooler, but with reference from the thermistor inside the package. Or do you need cooling AND heating from it?

 

[pavjayt]

Thanks for your reply. I need only cooling as the APD gets very hot at high gains at bias voltage. Any good reference TE cooler circuits?

 

[pavjayt]

post removed, a new thread is started for this..