AD524 Analog Devices, Inc., AD524 Datasheet - Page 19

• Manufacturer Part Number: AD524
• Description: Precision Instrumentation Amplifier
• Manufacturer: Analog Devices, Inc.

An instrumentation amplifier can be turned into a voltage-
to-current converter by taking advantage of the sense and
reference terminals, as shown in Figure 46.
COMMON
Figure 45. Use of Reference Terminal to Provide Output Offset
ANALOG
+V
–V
+IN
V
–IN
V
IN
S
IN
S
+
–
35V
1µF
12
2
3
1
C1
OFFSET
AD524
INPUT
GAIN TABLE
A B GAIN
0
0
1
1
TRIM
+V
–V
0
1
0
1
8
7
C2
S
S
10
1000
100
1
R1
10kΩ
AD711
10
6
SENSE
REF
K1 – K3 =
THERMOSEN DM2C
4.5V COIL
D1 – D3 = IN4148
9
1
2
3
4
5
6
7
8
PROTECTION
PROTECTION
20kΩ
AD524
20kΩ
A1
V
LOAD
OFFSET
20kΩ
Figure 47. Three-Decade Gain Programmable Amplifier
+V
S
20kΩ
20kΩ
INPUTS
RANGE
GAIN
20kΩ
+5V
4.44kΩ
Rev. F | Page 19 of 28
404Ω
A
B
40Ω
NC = NO CONNECT
16
15
14
13
12
11
10
1
2
5
7
3
4
6
9
10kΩ
DECODER
74LS138
R2
OUT
By establishing a reference at the low side of a current setting
resistor, an output current may be defined as a function of input
voltage, gain, and the value of that resistor. Because only a small
current is demanded at the input of the buffer amplifier (A2)
the forced current, I
drift specifications of A2 must be added to the output offset and
drift specifications of the AD524.
OUTPUT
OFFSET
TRIM
16
15
14
13
SHIELDS
RELAY
Y0
Y1
Y2
NC
+INPUT
–INPUT
K1
G = 10
I
K1
L
=
Figure 46. Voltage-to-Current Converter
R1
V
D1
X
=
L
13
2
3
1
, largely flows through the load. Offset and
V
R1
IN
G = 100
K2
+
–
AD524
K2
=
(
1 +
1
2
5
7
3
4
6
10
6
D2
SENSE
REF
40,000
BUFFER
DRIVER
AD711
7407N
R
G
G = 1000
K3
9
)
K3
A2
16
D3
R1
V
X
10µF
LOAD
LOGIC
COMMON
+5V
I
L
AD524