(Re-posted using a proper news provider, because i was told googlegroups is blocked by many on this list)
Hello everyone,
first post here. I hope I do not break any rule; let me know if this is the case.
Disclaimer: not native English speaker, forgive any mistake.
My background: master degree in physics (with a few courses in electronics). PhD in electronics/physics, doing 99% of digital design. My last encounter with analog design: 10 years ago (ie: my knowledge is a bit "rusty").
The problem: I work in high energy physics. Currently, my new project is to design a new version (in a new technology: from 250nm to 130nm) of a chip which has to perform current-to-frequency (CFC from now on) conversion. (for background information, if interested, you can read the previous designer work here:
Basically, I need to design a CFC with input currents ranging from 1nA to 1mA, with a 40 us integration window and low input leakage (target:
100fA). Other details can be provided if needed.The main problem is the design of the amplifier. I am studying the common designs and the usual architectures; BUT I have a difficult time in connecting the high-level specification of the device (CFC, min/max input current, etc..) with the low level specs of the amplifier (a fully differential OTA, if we keep the previous architecture) such as GBP, phase margin, slew rate, etc...
I understand that there is no such thing as a "magical" formula to design such circuits, but I assume that there must be, somewhere, a point from where to start, which is what I am missing here.
All the examples and designs I see (in tutorials or articles) start from the wanted specifications of the OpAmp, which would be good, if I had an idea on how to obtain them!
I hope that the question make sense to you.
Any help you can give is greatly appreciated!
thanks
Francesco