ISL28133_11 Datasheet, PDF (12/20 Pages) Intersil Corporation – Single Micropower, Chopper Stabilized, RRIO Operational Amplifier

ISL28133
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
0
30 60 90 120 180 240 300 360 420 480 540 600
TIME (DAYS)
FIGURE 37. LONG TERM DRIFT (V_OS vs TIME) FOR 30 UNITS
Long Term V_OS Drift
Figure 37 shows a plot of daily V_OS 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,
mounted on a single PC board and kept at room temp. The 30
amplifier outputs were measured daily by a DVM and scanner
under computer control. The daily V_OS measurements were
subtracted from the initial V_OS value to calculate the V_OS shift.
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 were
interpolated.
The change in amplifier V_OS over the 572 day period for all 30
amplifiers (see Figure 38) was less than ±100nV, and no clear
V_OS 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 V_OS errors, leaving only the V_OS
error contribution due to changes in the long term stability of the
external components (see Figure 39).
100kΩ
10Ω
+2.5V
-
10Ω
+
1kΩ
100kΩ
-2.5V
V_OUT
A_CL = 10kV/V
FIGURE 39. LONG TERM DRIFT TEST CIRCUIT
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
0
30 60 90 120 180 240 300 360 420 480 540 600
TIME (DAYS)
FIGURE 38. LONG TERM DRIFT (V_OS vs TIME) FOR A SINGLE UNIT
ISL28133 SPICE Model
Figure 40 shows the SPICE model schematic and Figure 41
shows the net list for the ISL28133 SPICE model. The model is a
simplified version of the actual device and simulates important
parameters such as noise, Slew Rate, Gain and Phase. The
model uses typical parameters from the ISL28133. The poles
and zeros in the model were determined from the actual open
and closed-loop gain and phase response. This enables the
model to present an accurate AC representation of the actual
device. The model is configured for ambient temperature of
+25°C.
Figures 42 through 49 show the characterization vs simulation
results for the Noise Density, Frequency Response vs Close Loop
Gain, Gain vs Frequency vs CL and Large Signal Step Response
(4V).
12
FN6560.5
July 22, 2011