Analog Channel Notes

A circuit diagram of a device
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Calculator for our levers

https://docs.google.com/spreadsheets/d/1VJTuBukCeR8GGBbfJELEy8z72eeXJkKCebAghGk4s7Q/edit?usp=sharing

Components

Reverse biased diode forms a depletion region as charges migrate
- Electron moves faster - induces curent
- Great for gamma ray detection
Charged particles (gammas from Bremsstrahlung radiation) deposit energy onto depletion region of photodiode.
- Produces an electron-hole pair due to:
Thermal excitation of photodiode material induces a dark current
- Source of our baseline
- When this baseline is too large, lose range in our channel

Standard non-inverting config
0-3.3V range
Gain will amplify our baseline and any noise!
- Gain provided by ratio of lower resistor network

Q = C * V
- Q is the charge from induced current from photodiode - constant
- V is the pulse we see that gets read by ADC (after amplification)
- Voltage pulse is inversely proportional to capacitance
Basically, capacitance inversely proportional to sensitivity
- smaller capacitance = more sensitive
  - low C → high V → bigger pulse to be read → more sensitive
- larger capacitance = less sensitive
  - high C → low V → smaller pulse to be read → less sensitive

V = I * R
- I is the current from diode
- V is the pulse we see that gets read by ADC
- Resistance proportional to baseline voltage
If R too high, baseline is too high, and our usable range is smaller
- Less sensitive sensor!