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Entry  Thu Mar 29 02:51:35 2018, Koji, Summary, BEAT, The design for a new beat PD  6x
    Reply  Mon Apr 2 00:15:34 2018, rana, Summary, BEAT, The design for a new beat PD  
       Reply  Wed Apr 4 02:06:45 2018, Koji, Summary, BEAT, First article of the CTN beat PD 7x
          Reply  Thu Apr 5 02:04:49 2018, Koji, Summary, BEAT, Compensation for MAX4107 at G=4.5 max_circuit.pdfIMG_3667.JPGIMG_3668.JPGIMG_3665.JPGCTN25_schematic_180404_KA.pdf
             Reply  Fri Apr 6 04:48:02 2018, Koji, Summary, BEAT, Compensation for MAX4107 at G=4.5 CTN25_transimpedance.pdfcurrent_noise_CTN25.pdfidet_CTN25.pdf
                Reply  Sun Apr 22 17:46:55 2018, awade, Summary, BEAT, Compensation for MAX4107 at G=4.5 D980454-01.pdf
Message ID: 2157     Entry time: Thu Mar 29 02:51:35 2018     Reply to this: 2161
Author: Koji 
Type: Summary 
Category: BEAT 
Subject: The design for a new beat PD  

DC photocurrent:
a few mA => A transimpedance of 1k Ohm will realize the output of ~a few V.
A few mA of DC current produces the shot noise photocurrent of 20~30pA/rtHz  

RF photocurrent: 
Resonant circuit resistance @25MHz: 100~300 Ohm.
Reduced to 100 by the shunt resistance of 150 Ohm
MAX4107 required minimum gain of 10 for the stability
-> Total Transimp. R=1K
-> Andrew said R=1K gives 13dBm output (1.4Vpk @25MHz)
-> This corresponds to 200 V/us of slewrate. This is ~40% of the full scale. (Too big)

input referred current noise ~ 12pA/rtHz ==> Shot noise intercept current ~0.44mA

 

If we reduce the shunt resistance to get the total transimpedance of 500Ohm
=> Beat output: 7dBm (0.7Vpk@25MHz, ~20% of the full slewrate)

input referred current noise ~24pA/rtHz ==> Shot noise intervept current ~ 1.8mA


Questions:

- Can we torelate this noise level (24pA/rtHz)?

- Or do we have MAX4106 (min gain 5), or something else for a replacement?
 

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