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Entry  Fri Jun 20 11:41:18 2014, Nichin, Update, Electronics, Transimpedence measurement-BBPD BBPD_readings_06-19-2014.zipBBPD_transimpedence_19thJune2014.pdf
    Reply  Fri Jun 20 19:09:23 2014, Koji, Update, Electronics, Transimpedence measurement-BBPD 
       Reply  Mon Jun 23 21:16:14 2014, Nichin, Update, Electronics, Transimpedence measurement-BBPD BBPD_transimpedence_06-23-2014.pdfBBPD_readings_06-23-2014.zip
Message ID: 10089     Entry time: Mon Jun 23 21:16:14 2014     In reply to: 10085
Author: Nichin 
Type: Update 
Category: Electronics 
Subject: Transimpedence measurement-BBPD 

  [Nichin, Koji] 

Today evening, me and koji decided to get down to the problem of why the trasimpedence plots were not as they were supposed to be for Broadband photodiode (D1002969-v8) S1200269. There were a few problems that we encountered:

  • Turns out the REF PD was not illuminated properly, for maximum output. The DC output voltage turned out to be much higher than the previous measurement. Since I assumed that the REF PD had not been touched since the first day I took readings, I did not check this.
  • The fork holding the Test PD was a bit out of shape and only one side of it was clamping down the PD. This made the PD vulnerable swivel about that one side. We replaced it with a new one.
  • I was setting the current diving the Jenne laser to about 20mA and this resulted in nocthes at higer frequencies in the network analyzer due to over driving of the diode laser. Once we reduced this to about 12.5-13 mA they disappeared. Also, the current limit setting was set at 40mA which is way too high for the jenne laser and might have resulted in damaging it if someone had accidentally increased the current. We have now set it at 20mA.

After these changes the measurements are as follows:

I moved the NA from near rack 1Y1 to the Jenne laser table. 

 Acquiring data

  • Jenne Laser driving current: 12.8mA 
  • The following conditions were set on Network Analyzer Agilent 4395:


1) Frequency sweep range: 1MHz to 300 MHz.

2) Number of Points sampled in  the range: 801

3) Type of sweep: Logarithmic

  • Set the NA to give the corresponding transfer function value (output of BBPD over output of 1611) and also Phase response in degrees.
  • Save the data into floppy disk for processing on the computer.


DC output voltage of REF PD: 0.568V

DC output voltage of BBPD: 18mV

Power incident on REF PD and BBPD respectively: 0.184mW  and 0.143mW

Hence, Responsivity for REF PD and BBPD respectively:  0.315 A/W and 0.063 A/W 

Responsivity given in the Datasheet for REF PD and BBPD : 0.68 A/W and 0.1 A/W



The reason for these differences are unknown to me and must be investigated.

The Plots of transimpedence obtained are attached. The data and matlab code used is in the zip file.

The transimpedance of  Broadband photodiode (D1002969-v8) S1200269 was around 1kV/A-2kV/A for most of the range, but the value started falling as the frequency approached 100 MHz. This BBPD is best when used at 10-30 MHz.

Attachment 1: BBPD_transimpedence_06-23-2014.pdf  7 kB  | Hide | Hide all
Attachment 2: BBPD_readings_06-23-2014.zip  17 kB
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