AD707AR AD [Analog Devices], AD707AR Datasheet - Page 8

• Manufacturer Part Number: AD707AR
• Description: Ultralow Drift Op Amp
• Manufacturer: AD [Analog Devices]

AD707
PRECISION CURRENT TRANSMITTER
The AD707’s excellent dc performance, especially the low offset
voltage, low offset voltage drift and high CMRR, makes it
possible to make a high precision voltage-controlled current
transmitter using a variation of the Howland Current Source
circuit (Figure 26). This circuit provides a bidirectional load
current which is derived from a differential input voltage.
0.370 (9.40)
0.335 (8.51)
0.335 (8.51)
0.305 (7.75)
0.040 (1.02) MAX
0.200 (5.08)
0.125 (3.18)
Figure 26. Precision Current Source/Sink
0.045 (1.14)
0.010 (0.25)
(5.08)
0.200
MAX
V
0.185 (4.70)
0.165 (4.19)
0.005 (0.13) MIN
PIN 1
IN
(1.27)
0.023 (0.58)
0.014 (0.36)
0.050
MAX
8
100k
100k
1
0.405 (10.29) MAX
R3
R1
0.250 (6.35)
0.750 (19.05)
0.500 (12.70)
0.100
(2.54)
BSC
MIN
0.019 (0.48)
0.016 (0.41)
REFERENCE PLANE
8-Pin Metal Can
BASE & SEATING PLANE
0.055 (1.4) MAX
8-Pin Cerdip
0.070 (1.78)
0.030 (0.76)
2
3
0.021 (0.53)
0.016 (0.41)
t
(H-08A)
L
5
4
= –––––––
(Q-8)
AD707
R
0.310 (7.87)
0.220 (5.59)
0.060 (1.52)
0.015 (0.38)
SCALE
V
+V
–V
(5.08)
0.200
BSC
IN
4
7
S
S
SEATING
PLANE
0.150
(3.81)
MIN
0.100
(2.54)
100k
100k
BSC
R4
R2
( )
0.1µF
0.1µF
R2
–––
R1
3
6
4
2
(2.54)
0.100
BSC
0.320 (8.13)
0.290 (7.37)
15
0.015 (0.38)
0.008 (0.20)
0
5
1
0.034 (0.86)
0.027 (0.69)
R
R
I
L
L
SCALE
Dimensions shown in inches and (mm).
6
8
BSC
45
7
OUTLINE DIMENSIONS
0.160 (4.06)
0.110 (2.79)
0.045 (1.14)
0.027 (0.69)
–8–
The performance and accuracy of this circuit will depend almost
entirely on the tolerance and selection of the resistors. The scale
resistor (R
the accuracy of the load current and should be chosen carefully
or trimmed.
As an example of the accuracy achievable, assume I
10 mA, and the available V
R
I
Low drift, high accuracy resistors are required to achieve high
precision.
ERROR
SCALE
Maximum I
= 130 A/10 mA = 1.3% @ 25 C
= 180 A/10 mA = 1.8% @ 125 C
0.210 (5.33)
0.160 (4.06)
0.115 (2.93)
due to the AD707C:
= 10 mV/10 mA = 1
0.1574 (4.00)
0.1497 (3.80)
0.0098 (0.25)
0.0040 (0.10)
SEATING
0.022 (0.558)
0.014 (0.356)
SCALE
PLANE
MAX
ERROR
PIN 1
) and the four feedback resistors directly affect
0.1968 (5.00)
0.1890 (4.80)
0.0500
0.430 (10.92)
(1.27)
8
BSC
0.348 (8.84)
8
1
1
PIN 1
0.100
(2.54)
BSC
= 2(V
= 2 (15 V)/l
= 30 A + 0.2 A/ C + 100 A
0.0192 (0.49)
0.0138 (0.35)
8-Pin Plastic DIP
0.0688 (1.75)
0.0532 (1.35)
5
4
0.070 (1.77)
0.045 (1.15)
4
5
8-Lead SOIC
I
+ 1 nA (100 k)/l
(150 A @ 125 C)
OS
0.2440 (6.20)
0.2284 (5.80)
IN
0.060 (1.52)
0.015 (0.38)
OS
0.280 (7.11)
0.240 (6.10)
(SO-8)
(N-8)
is only 10 mV.
)/R
(100 k/R
SCALE
0.0098 (0.25)
0.0075 (0.19)
0.130
(3.30)
MIN
SEATING
PLANE
+2 (0.1 V/ C)/l
SCALE
+ 2(V
0.325 (8.25)
0.300 (7.62)
8
0
)
0.015 (0.381)
0.008 (0.204)
OS
0.0196 (0.50)
0.0099 (0.25)
(1.5 nA @ 125 C)
0.0500 (1.27)
0.0160 (0.41)
Drift)/R
0.195 (4.95)
0.115 (2.93)
L
must be
x 45
SCALE
REV. B
+