Datasheet

AD8628/AD8629/AD8630
Rev. I | Page 17 of 24
TIME (500µs/DIV)
VOLTAGE (V)
V
OUT
0V
0V
V
IN
02735-056
CH1 = 50mV/DIV
CH2 = 1V/DIV
A
V
= –50
Figure 59. Negative Input Overload Recovery for the AD8628
TIME (500µs/DIV)
VOLTAGE (V)
V
OUT
0V
0V
V
IN
02735-057
CH1 = 50mV/DIV
CH2 = 1V/DIV
A
V
= –50
Figure 60. Negative Input Overload Recovery for Competitor A
TIME (500µs/DIV)
VOLTAGE (V)
V
OUT
0V
0V
V
IN
02735-058
CH1 = 50mV/DIV
CH2 = 1V/DIV
A
V
= –50
Figure 61. Negative Input Overload Recovery for Competitor B
The results shown in Figure 56 to Figure 61 are summarized in
Table 5.
Table 5. Overload Recovery Time
Model
Positive Overload
Recovery (μs)
Negative Overload
Recovery (μs)
AD8628 6 9
Competitor A 650 25,000
Competitor B 40,000 35,000
INFRARED SENSORS
Infrared (IR) sensors, particularly thermopiles, are increasingly
being used in temperature measurement for applications as wide
ranging as automotive climate control, human ear thermometers,
home insulation analysis, and automotive repair diagnostics.
The relatively small output signal of the sensor demands high
gain with very low offset voltage and drift to avoid dc errors.
If interstage ac coupling is used, as in Figure 62, low offset and
drift prevent the output of the input amplifier from drifting close to
saturation. The low input bias currents generate minimal errors
from the output impedance of the sensor. As with pressure sensors,
the very low amplifier drift with time and temperature eliminate
additional errors once the temperature measurement is calibrated.
The low 1/f noise improves SNR for dc measurements taken
over periods often exceeding one-fifth of a second.
Figure 62 shows a circuit that can amplify ac signals from 100 µV to
300 µV up to the 1 V to 3 V levels, with a gain of 10,000 for
accurate analog-to-digital conversion.
5V
100kΩ10k
Ω
5V
100µV TO 300µV
100Ω
TO BIAS
VOLTAGE
10kΩ
f
C
≈ 1.6Hz
IR
DETECTOR
100kΩ
10µF
1/2 AD8629
1/2 AD8629
02735-059
Figure 62. AD8629 Used as Preamplifier for Thermopile