Datasheet

Data Sheet AD627
Rev. E | Page 17 of 24
Table 7. Maximum Gain for Low Common-Mode, Single-Supply Applications
V
IN
REF Pin Supply Voltage R
G
(1% Tolerance) Resulting Maximum Gain Output Swing WRT 0 V
±100 mV, V
CM
= 0 V 2 V 5 V to 15 V 28.7 kΩ 12.0 0.8 V to 3.2 V
±50 mV, V
CM
= 0 V 2 V 5 V to 15 V 10.7 kΩ 23.7 0.8 V to 3.2 V
±10 mV, V
CM
= 0 V 2 V 5 V to 15 V 1.74 kΩ 119.9 0.8 V to 3.2 V
V− = 0 V, V+ = 0 V to 1 V 1 V 10 V to 15 V 78.7 kΩ 7.5 1 V to 8.5 V
V− = 0 V, V+ = 0 mV to 100 mV 1 V 5 V to 15 V 7.87 kΩ 31 1 V to 4.1 V
V− = 0 V, V+ = 0 mV to 10 mV 1 V 5 V to 15 V 787 Ω 259.1 1 V to 3.6 V
Table 8. RTI Error Sources
Maximum Total RTI Offset Error (μV) Maximum Total RTI Offset Drift (μV/°C) Total RTI Noise (nV/√Hz)
Gain AD627A AD627B AD627A AD627B AD627A/AD627B
[phone]
[phone]
[phone] 3.5 1.5 39
[phone] 3.2 1.2 38
+100
270
155
3.1
1.1
38
[phone]
[phone]
Table 7 gives values for the maximum gain for various single-
supply input conditions. The resulting output swings refer to
0 V. To maximize the available gain and output swing, set the
voltages on the REF pins to either 2 V or 1 V. In most cases,
there is no advantage to increasing the single supply to greater
than 5 V (the exception is an input range of 0 V to 1 V).
OUTPUT BUFFERING
The AD627 is designed to drive loads of 20 kΩ or greater but
can deliver up to 20 mA to heavier loads at lower output voltage
swings (see Figure 10). If more than 20 mA of output current is
required at the output, buffer the AD627 output with a precision
op amp, such as the OP113. Figure 40 shows this for a single
supply. This op amp can swing from 0 V to 4 V on its output
while driving a load as small as 600 Ω.
V
IN
R
G
+V
S
–V
S
AD627
0.1µF
0.1µF
0.1µF
–V
S
V
OUT
REF
0.1µF
OP113
00782-038
Figure 40. Output Buffering
INPUT AND OUTPUT OFFSET ERRORS
The low errors of the AD627 are attributed to two sources,
input and output errors. The output error is divided by G when
referred to the input. In practice, input errors dominate at high
gains and output errors dominate at low gains. The total offset
error for a given gain is calculated as
Total Error RTI = Input Error + (Output Error/Gain) (5)
Total Error RTO = (Input Error × G) + Output Error (6)
RTI offset errors and noise voltages for different gains are listed
in Tabl e 8.