40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  PSL  Not logged in ELOG logo
Message ID: 2368     Entry time: Mon Jul 22 16:17:08 2019
Author: ScottA 
Type: DailyProgress 
Category: TempCtrl 
Subject: TIA Op-amp for AD590 Temp Circuit 

Background:

Here I have used zero to model the effect of replacing OPA827 with other op-amps for the transimpedance amplifier stage of the AD590 temperature sensing circuit. The graph shows the sum of the noise at the output of the circuit right before the ADC.

The table shows the typical input offset voltage drift for each component. I have ordered the table from the lowest noise to the highest at 1 millihertz. 

The library of op-amps I used is from the develop branch of zero, which should be available on master soon.

 

 

Candidates (* used now)
(Output Voltage Noise Ordered low to high from 1e-3) 
Typ Drift [uV/°C]
1. AD811_G10

5

2. AD8671  .3
3. CS3001 .05
4. LT1128   .25
5. LT1037 .6
6. LT1124  .4
7. OP270  1
8. TLE2227  .4
9. AD797 .2
10. AD829  .3
11. AD8675 .2
12. *OPA827 .1
13. OP284     .2

 

Results:

From what I can see the two best candidates to replace OPA827 would be AD8671 or LT1128, as they have an all-around lower noise density than OPA827. OPA827 does have the smallest temperature drift of all the op-amps though, so it depends on what we care more about.

Attachment 1: AD590_Diff_OpAmps_Noise_Budget.pdf  34 kB  Uploaded Mon Jul 22 17:17:57 2019  | Hide | Hide all
AD590_Diff_OpAmps_Noise_Budget.pdf
Attachment 2: Zero_AD590_Noise_Budget_Different_Op_Amps.zip  486 kB  Uploaded Tue Jul 23 00:58:10 2019
Attachment 3: AD590_Diff_OpAmps_Noise_Budget_v2.pdf  35 kB  Uploaded Tue Jul 23 00:59:04 2019  | Hide | Hide all
AD590_Diff_OpAmps_Noise_Budget_v2.pdf AD590_Diff_OpAmps_Noise_Budget_v2.pdf
ELOG V3.1.3-