Hi:
I'm contemplating the design of an amplified photodiode instrument that should be able to bias a photodiode for photoconductive operation, and provide a positive voltage output of at least 0-10V into a high-Z load. There would likely be three stages of active circuitry, a transimpedance amp, an adjustable extra gain stage, and a buffer/line-driver. Max bandwidth of about 10MHz. I won't be optimizing the design for noise other than making sure power is clean, the board layout is decent, mid-range parts with fairly low-noise as well as low-power are chosen, and the circuitry is enclosed in a metal can for shielding. This does not need to be a "shot-noise limited" design, a task that is beyond my capabilities.
It would be preferable to power it with a single 9V battery. However, to meet the specs, this would then require some DC/DC conversion to make a split supply for ease of op-amp circuitry. Or perhaps I'd power from 2x9V batts, and just use a switched-cap chip to generate -V for the first transimpedance stage. That way the DC/DC could be less complicated and not need to supply much power.
But can a DC/DC be incorporated in a way that will not substantially increase the noise of the system? In other words, would you even consider putting any form of DC/DC into a can with a photodiode amp, and expect to avoid adding any noise to the system that would not have originally been present?
If it hopeless to avoid adding noise by putting a DC/DC into the can then I'll have to settle for a remote split DC supply fed by a cable.
Thanks for input.