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Entry  Tue Jan 22 17:29:29 2013, Riju, Update, , Photodiode transimpedance pda255shotnoiseintercept.pdf
    Reply  Tue Jan 22 19:51:52 2013, Koji, Update, , Photodiode transimpedance 
       Reply  Wed Jan 23 11:43:19 2013, Riju, Update, , Photodiode transimpedance pda255shotnoiseintercept1.pdf
Message ID: 7929     Entry time: Wed Jan 23 11:43:19 2013     In reply to: 7927
Author: Riju 
Type: Update 
Category:  
Subject: Photodiode transimpedance 

Quote:

- The data should be plotted in a log-log scale.
- The data points were only taken in the high current region.

- The plot may suggest that the amplifier saturate at the RF.

PDA255 has the nomial transimpedance gain of 10^4 Ohm.
The DC current of 10^-3 gives the output of 10V.
This plot may tell that the saturation starts even at the 1/10 of the full DC range.

The plot doesn't have many points below 0.1mA.
Consult with my plots for the similar measurements.
The measured points are logarithmically spaced. Use the same technique.

- It is also very unknown that how the noise level is calculated. No info is supplied in the plot or the elogs.

 Here I am attaching the plot in loglog scale. I have taken the data-points from no light condition to the maximum light condition, the minimum variation possible in the current supply was 0.01A. The noise was visibly decreasing at higher light level.

For the noise level calculation I took the average of total noise in the range 7-60MHz. For each range the formula used was

noisevalue= sqrt(data(:,2)*100)/sqrt(2)/sqrt(channel BW);     -- this conversion is needed since the data was collected in the 2 column format: frequency, spectrum(W).

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