Greetings, I'm a physicist way in over my head with some circuit design and could use some help. We want to retrofit a high speed photodiode amplifier into an existing atomic force microscope. The present amplifier has a bandwidth of 900 kHz and but we are interesting in signals up to 10 MHz. I have already taken a stab at it but could really use some help.
Constraints:
Available power: +-15V
Signal fed to 10V ADC
Diode sensitivity: 0.36A/W
Diode capacitance: 45pF (0V reverse bias), 9pF (5V reverse bias)
Laser: <=1mW @ 690nm
My attempted solution uses the
LT1226, the fastest amplifier with +-15V rails I could find. It is a simple low gain transimpedance amplifier for the first stage. The gain has been set low so that the compensation doesn't wreck the bandwidth. The second stage is pure gain to boost the expected max signal (roughly) up to 10V, no compensation needed since the 80R shields it from seeing any capacitance (I think).
My main concern is, will this thing be stable? So far as I can tell, yes, but maybe I missed something. But as I mentioned, I am a total noob in this area, so I am looking forward to hearing any and all feedback y'all have to offer. If you have tips on how to potentially go faster, I'm all ears.