AD694 Analog Devices, AD694 Datasheet - Page 12

• Manufacturer Part Number: AD694
• Description: 4.20 mA Transmitter
• Manufacturer: Analog Devices

AD694
The AD694 will now output a 4-20 mA output current for a 0
to 2 V differential swing across V
end is adjusted so that the desired full-scale input signal at V
results in a V
full scale will require a gain of 20 in the front end. The gain is
determined according to the equation:
The circuit shown, will convert a positive differential signal at
V
of 3 V to 8 V. The low end of the common-mode range is limited
IN
to a 4-20 mA current. The circuit has common-mode range
16-Lead Cerdip
A
(Q) Package
of 2 V. For example a sensor that has a 100 mV
G = [2R
S
/Rg] + 1
A
. The gain of the in amp front
Figure 15. Low Cost Sensor Transmitter
Dimensions shown in inches and (mm).
OUTLINE DIMENSIONS
16-Lead Plastic DIP
(N) Package
IN
–12–
by the AD708’s ability to pull down on R
plifier could be used instead to extend the common-mode range
down to about 1.5 V.
As shown, the circuit handles positive differential signals, (V
positive). To handle bipolar differential signals (V
or negative), the reference pin of the in amp (point C) must be
offset positively from the 2 V reference. For example, discon-
nected point C from the 2 V reference and connecting it to a
3 V source would result in a V
volt differential input from the sensor.
16-Pin SOIC (R) Package
A
of 1 V, (or half scale) for a zero
S
. A single supply am-
IN
is positive
REV. A
IN