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Message ID: 2399     Entry time: Wed Aug 14 19:50:37 2019
Author: Shalika Singh 
Type: Noise Budget 
Category: 2micronLasers 
Subject: Noise analysis of Sallen Key filter using SR785 and Zero simulation 

The photodiode needs a 1V bias so for a clean bias we have decided to use a sallen key low pass filter with a cut off frequency at 1Hz. The quality factor of the designed sallen key filter is 0.707.

Attachment 1: The Circuit Diagram of Sallen Key filter

The gain of the circuit is 1. 

Attachment 2: The transfer function of the filter

We can see the cut off frequency at 1Hz

Attachment 3: The Input Referred Noise of filter

The input-referred voltage noise was obtained using SR785 and compared with zero simulation. It deviates a lot from the simulated results by a factor of 100.

Attachment 4: Scripts

Find all the data and scripts used for the measurements.

NOTE: Noise plot below had inconsistent units; please ignore.

 

Attachment 1: sallenkeyfilter.pdf  239 kB  Uploaded Wed Aug 14 20:51:25 2019  | Hide | Hide all
sallenkeyfilter.pdf
Attachment 2: Transfer_function_of_sallen_key.pdf  13 kB  Uploaded Wed Aug 14 21:17:22 2019  | Hide | Hide all
Transfer_function_of_sallen_key.pdf
Attachment 3: Noise_across_SallenKey.pdf  67 kB  Uploaded Wed Aug 14 21:17:56 2019  | Hide | Hide all
Noise_across_SallenKey.pdf
Attachment 4: sallenkey.zip  103 kB  Uploaded Thu Aug 15 23:13:54 2019
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