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Message ID: 7984     Entry time: Fri Feb 1 14:47:17 2013
Author: Riju 
Type: Update 
Category:  
Subject: Photodiode transimpedance 

 Summary: Measurement and plot of shot-noise-intercept-current for MC REFL PD. 

Motivation:It is to measure the shot noise intercept current for MC REFL PD.

 

Result: The final plot is attached here. The plot suggests that the value of shot-noise-intercept current is 0.041mA

Discussion:

 

The plot is for the measured data of Noise voltage (V/sqrt(Hz)) vs DCcurrent(A). The fitted plot to this measured data follows the noise equation

Vnoise = gdet* sqrt[ 2e (iDC+idet)] ,  where gdet= transimpedance of the PD in RF region as described in manual of PDA255 (i.e. 5e3 when it is not in High-impedance region).

To get an approximate idea of the shot noise intercept current, we may follow the same procedure described in 7946 

In the present case minimum noise value is 2.03e-08 V/sqrt(Hz)

Therefore dark current(in2) ~dark noise voltage/RF transimpedance = 4.06pA/sqrt(Hz)

Therefore the approximate shot noise intercept current value is (4/18)^2 ~ 0.049mA, which is close to the fitted value.

 

 ... hard to believe these numbers. Wrong DC transimpedance? (KA)

Attachment 1: shotnoiseinterceptmcreflpd.pdf  6 kB  | Hide | Hide all
shotnoiseinterceptmcreflpd.pdf
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