ADC question

[llamoure]

Hello All,

I'm currently performing an experiment in quantum optics that requires me to measure the intensity of a laser beam using a fast (2GHz) photodetector (THORLABS model DET01CFC). The photodetector outputs a current of maximum 100mA.

I would like to digitize into a stream of binary numbers a voltage proportional to this current using the proper analog to digital converter. When I say proper, I mean with maximum resolution and maximum sampling rate. THORLABS recommends using a 50 Ohms resistor at the opposite end of the detector (in this case the ADC) in order to maximize the bandwidth.

Can anyone suggest to me a company and/or model of an ADC that could suite the above requirements? I've been looking through different providers (Analog Devices, etc) but nothing seems to be compatible with what I would like to have.

Thanks in advance!

Louis

http://quic.ulb.ac.be/members/louis

 

[geekEE]

You say that you want maximum resolution and maximum sampling rate. What is the minimum resolution and sampling rate that is acceptable? The really fast ADCs are flash converters, which typically don't have more than about 8 bits of resolution. For example, National has the ADC081000 which is a 1 GSPS 8-bit converter. You will probably have to interleave multiple converters if you want faster rates.

Glenn

 

[Higgler]

There are flash ADC's that my company used 10 years ago at 2.4 GHz. Can't recall who made them, TRW maybe. Expensive hardware. I don't think standard off the shelf ADC'a are at 2 GHz yet. Standard speed 10 years ago was 800 MHz.

IF you haven't had alot of experience laying out a high speed circuit board, get some expert help. That's pretty fast and it's far from trivial to plunk down a 2 GHz IC and make it work well. Often requires expensive software to lay out and optimize the circuit.

kch
Here's a note on TRW's latest ADC speed, 3 GHz.

A 10-bit, three giga-sample ADC, for example, samples an analog signal at the rate of three billion samples per second.

I'd expect the cost is extremely high.

 

[VEBill]

You might want to investigate what sort of ADC hardware they use at CERN and similar particle labs. Somebody somewhere must have written a paper describing the exact hardware used. I expect that their requirements are very similar in nature to yours. At the least, you'll see what defines the state-of-the-art at that time.

 

[itsmoked]

I'd be willing to bet you need a professional who has done fast A2Ds before. You won't be pulling this off in less than a year and three design cycles otherwise. I also suspect that TRW part will cost at least $3K for one IC.

Keith Cress
kcress -

http://www.flaminsystems.com