[Ronja] Increasing the RX sensitivity and range

[Karel Kulhavy]

I have developed a new method to calculate noise. Noise is not expressed in amperes or volts per square root of Hertz (which is difficult to calculate with and to imagine),
but as a DC current which causes shot noise.

Then it's very simple:
diode with current I flowing -> I (including photodiode)
transistor base -> Ib
transistor collector -> Ic
resistor: 52mV/R
MOSFET drain: 34mV * gs (forward transfer admittance or transconductance)
amplifier with gain A -> increases or decrases by A^2

Then the 100k resistor in Ronja input makes 500nA and the MOSFET only 274nA. The
dark current makes 5nA.

If we connect the diode to 48V, we reduce the total input
capacitance from 5pF to 3.8pF which increases the signal by 30%. We can icnrease the
feed resistor to 390 kOhm which reduces the resistor noise to 130nA!

If you are bored, please try connecting the diode to 48V through a 390 kOhm instead of 12V through 100kOhm and tell if the distance during low ambient light increases. Don't forget copious filtering and shielding for the 48V. The input is extremely sensitive!

This should increase the range during low light conditions (fog during the night).

I will recalculate this all anyway because I am attempting to build a new better Ronja
RX. I am just curious if someone wants to try it earlier than me! :)

Karel