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Message ID: 1179     Entry time: Mon Nov 29 19:42:23 2010
Author: Alastair 
Type: Electronics 
Category: GYRO 
Subject: photodiode plans 

 Here is the plan for our generic PD board.  It is designed to be used in three different readout configurations:

1) Transimpedance amplifier

2) Resonant PD (using capacitance of the photodiode in resonant circuit)

3) Resonant notch readout.

IC4 is the main RF readout.  The inputs have jumpers to allow it to be connected in either inverting or non-inverting configuration.  The output of this goes either directly to the output of the box (for transimpedance readout) or can go to IC5 which will be an RF amplifier (probably from this company).

IC3 gives DC readout (except for transimpedance design) using a transimpedance setup to connect L1 to ground.  At very high frequencies we bypass this using a capacitor to ground.

The diode is biased through a resistor giving a second DC readout option.  IC1 reads out the voltage across this resistor differentially.  Frank suggested using the setup with IC2 to keep the voltage at the photodiode constant (otherwise when the photocurrent changes, the voltage drop across the resistor will also change causing a change in diode bias).

Attachment 1: photodiode_diagram.pdf  965 kB  | Hide | Hide all
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