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Entry  Wed Jul 6 16:40:09 2016, Aakash, Update, General, Seismometer Enclosure Development | SURF 2016 AD592CNZ_avg.pngAD592CNZ_diff.png
    Reply  Wed Jul 6 20:51:00 2016, Koji, Update, General, Seismometer Enclosure Development | SURF 2016 
Message ID: 12256     Entry time: Wed Jul 6 20:51:00 2016     In reply to: 12253
Author: Koji 
Type: Update 
Category: General 
Subject: Seismometer Enclosure Development | SURF 2016 

Circuit1: It is nice to receive the voltage across the transimpedance resistor with a high impedance buffer (or amplifier), as close to the resister as possible. This amplifier needs to have low numbers for input bias current, input offset current, and input current noise. These current noise becomes the noise of the temperature reading. On the top of that, the input voltage noise of the buffer will be added to the output. The typical noise model can be found in http://www.analog.com/media/en/technical-documentation/application-notes/AN-940.pdf

The good candidates for the buffer is LT1128, ADA4004, OPA140, and LT1012. If the application is not too sensitive to the total noise, OPA604 is a good choise with easier handling.

Circuit2: With the same reason, AD741 is an old generic amp that is not a great choise for this purpose. The current noise is more significant because of the higher transimpedance here. The same noise model as above can be used to analyze the performance.

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