bodokaiser / position-sensitive-detector

Position-sensitive detector with spatial resolution < 2.5 um.

Position-sensitive detector

Position-sensitive detector using the Hamamatsu S5991-01 position-sensitive photodiode.

Parameter	Value
Spatial resolution	2 um
Bandwidth	1400 kHz
Input voltage	+- 15 V
Output voltage	+- 12 V

position-sensitive-detector's Issues

Todos

Measurement errors

• precision vs. accuracy

Photonic

Refers to the random nature of incident photons.

• shot (Poisson distributed) noise
• background light noise

room light	1070 nm	532 nm	456 nm
on	152 uW	182 uW	243 uW
mostly off	0.12 uW	0.16 uW	0.28 uW

This refers only to mean of the background light, however, we are interested in the variance thereof.

Photodiode

Refers to noise sources of the semiconductor detector as a whole.

• allocation along terminals (multivariate binomial distributed)
• thermal (Johnson) noise
• shot noise

Transimpedance amplifier

• input current noise equivalent
• input voltage noise equivalent
• thermal noise feedback resistor

Miscellaneous

Offset compensation

• thermal (Johnson) noise
• common mode rejection
• preamp vs final
  -> Discuss the general procedure
  -> Because of precision first we will avoid additional components

Summing and difference amplifier

• common mode rejection
• crosstalk
  -> estimate noise contribution due to CMR and crosstalk
  -> decide if that noise is lower than usual op-amp noise

Experimental IoT

Connect PSD with local network via ethernet. Requires:

• STM32F0 ARM M0 Cortex microcontroller
• differential amplifier before ADC
• ethernet SPI controller with driver

Revisions

In this issue, we collect the improvements made to the design after building one revision.

Revision 0

• M2.5 for drill holes
• modular design
• copper planes
• mechanical stable power connector
• replace Electrolyt with MLCC caps
• larger MLCC package size
• add more and better test points

Revision 1

• fix footprint of OPA197, OPA2197

Revision 2

• denote revision on board
• use two dual-opamps for the transimpedance amplifiers
• use larger package for high capacities (e.g. 22u as 1206)
• use larger package for high power resistors (e.g. 1k, 120)
• use larger footprint than (TSSOP-14) for OPA4197 (TSSOP-14 is very error prone to solder)
• label power input (+15 V, GND, - 15 V) and connector output (DIFFX, DIFFY, SUM)
• label pins in signal and power headers
• fix pin numbers of signal header in PCB layout
• reposition R27, C23 on arithmetic PCB to reduce risk of interchange (check other components too)
• increase feedback resistors from buffer board to 4k (so in case the op amps saturate at +- 12V the expensive adc does not damage)
• supply voltage reference with voltage from regulators
• add pin test point to connect oscilloscope probe