Hi Richard, I've searched extensively on the net for various schematics for PMT preamps but apart from your design there's been zero success, but then I may be searching the wrong places!!!. I located a Nat Semi application note 301 on their website which gives a circuit for a switch mode supply and a signal conditioning circuit using the LF412 dual op amp to set supply volts and amplify/condition the PMT output. They go on to mention these tubes have a possible bandwidth approaching 1 GHz and a linear response range of around 100 million. Apart from that I'm kind of in the dark right now about what sorts of gain and characteristics a preamp circuit should have, apart from the fact that PMT's are current output devices. I suspect most op amp manufacturers would be fairly optimistic in using their devices (But then thats what app notes are for) to amplify such a fast signal and I'm working on the assumption that the weakest link in the whole chain will be the digital counter hooked up to the preamp and comparator/discriminator circuit. I'm planning on using a 1 gig frequency counter in period mode to count the pulses and I hope that will be fast enough to count events properly. The main reason for picking the LM359 is that it's cheap, fast is a current mode device and the app notes list a video amplifier and a fast photodiode amplifier (silicon though) as some of it's uses. I hope to expand that to medium quality PMT performance use.
Created on Friday, June 15, 2001 6:55 AM EDT by Mark G Harriss