Application Note 1729 Author: Bob Pospisil ISL28133 Long Term Drift Figure 2 shows a plot of daily VOS drift measurements of 30 individual ISL28133 amplifiers over a continuous 572 day period at +25°C. The 30 units were connected in a gain of 10k (see Figure 3), mounted on a single PC board and kept at room temperature. The 30 amplifier outputs were measured daily by a DVM and scanner under computer control. The daily VOS measurements were subtracted from the initial VOS value to calculate the VOS shift from zero-hour. The test board was powered from a UPS to maintain uninterrupted power to the test units. Three instances of lost measurement data ranging from 2 days to 2 weeks due to power loss to the measurement scanner were detected, and data was interpolated. 100k +2.5V 10 10 VOUT + 1k -2.5V 100k ACL = 10kV/V FIGURE 1. LONG TERM DRIFT TEST CIRCUIT The change in amplifier VOS over the 572 day period for all 30 amplifiers (see Figure 2) was less than ±100nV, and no clear VOS long term drift trend was evident in the data. The excellent long term drift performance is a result of the chopper amplifier’s ability to measure and correct VOS errors, leaving only the VOS error contribution due to changes in the long term stability of the external components. 1.0 0.8 0.6 VOS (µV) 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510 540 570 600 450 480 510 540 570 600 TIME (DAYS) FIGURE 2. LONG TERM DRIFT (V OS vs TIME) FOR 30 UNITS 1.0 0.8 0.6 VOS (µV) 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 TIME (DAYS) FIGURE 3. LONG TERM DRIFT (VOS vs TIME) FOR A SINGLE UNIT March 5, 2012 AN1729.0 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. Copyright Intersil Americas Inc. 2012. All Rights Reserved. 1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries. All other trademarks mentioned are the property of their respective owners. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com