hi,
can anyone help me in building preamplifier circuit? the signal that is going to be received has 30 nanosecond pulse width. any help will be appreciated.
hi,
its current. my concern is basically what type of op amp should i use? should it has high slew rate? if yes, what slew rate should it have? secondly i'm using S1223 pin photodiode. will it work for detecting such signal i.e 30 nanosecond?
Absolutely not! They are far too slow. Hamamatsu devices are fine but for that speed you need something smaller. Have a look at the selection guide **broken link removed** and look for something 300MHz or more.
You want to detect a 30ns pulse. That is a fast pulse and you need a fast photodiode to see it. It is all relative. A phototransistor may have a response time of several microseconds so wouldn't see a 30ns pulse at all.
I believe a good fast charge amplifier with a photodiode in the photoconductive mode is a nice solution. The diode is reverse biased into the charge amp. You can null the dark current by using a second similar diode. There is a pretty good reference circuit somewhere on the Analog devices website for a 10nS rise time amp using an HP diode.