AD524B AD [Analog Devices], AD524B Datasheet - Page 12

• Manufacturer Part Number: AD524B
• Description: Precision Instrumentation Amplifier
• Manufacturer: AD [Analog Devices]

AD524
PROGRAMMABLE GAIN
Figure 41 shows the AD524 being used as a software program-
mable gain amplifier. Gain switching can be accomplished with
mechanical switches such as DIP switches or reed relays. It
should be noted that the “on” resistance of the switch in series
with the internal gain resistor becomes part of the gain equation
and will have an effect on gain accuracy.
The AD524 can also be connected for gain in the output stage.
Figure 42 shows an AD711 used as an active attenuator in the
output amplifier’s feedback loop. The active attenuation pre-
sents a very low impedance to the feedback resistors, therefore
minimizing the common-mode rejection ratio degradation.
COMMON
ANALOG
+V
–V
+IN
–IN
S
S
1 F
35V
C1
OFFSET
INPUT
GAIN TABLE
A B GAIN
0
0
1
1
TRIM
0
1
0
1
C2
10
1000
100
1
R1
10k
K1 – K3 =
THERMOSEN DM2C
4.5V COIL
D1 – D3 = IN4148
1
2
3
4
5
6
7
8
Figure 41. Three Decade Gain Programmable Amplifier
20k
PROTECTION
PROTECTION
20k
AD524
A1
20k
+V
S
20k
20k
INPUTS
RANGE
GAIN
20k
+5V
4.44k
A
B
404
40
NC = NO CONNECT
16
15
14
13
12
11
10
–12–
9
DECODER
10k
74LS138
OUT
R2
+V
–V
–IN
+IN
1 F
OUTPUT
OFFSET
TRIM
S
S
35V
OFFSET
(+INPUT)
(–INPUT)
SHIELDS
INPUT
NULL
RELAY
Y0
Y1
Y2
AD711
NC
Figure 42. Programmable Output Gain
10k
K1
G = 10
K1
+V
–V
1
2
3
4
5
6
7
8
S
S
10pF
D1
20k
PROTECTION
PROTECTION
20k
AD524
G = 100
K2
20k
K2
20k
+V
S
V
D2
DD
V
BUFFER
DRIVER
SS
7407N
A2 A3 A4 WR
AD7590
20k
20k
G = 1000
K3
V
K3
20k
DD
4.44k
GND
404
40
D3
16
15
14
13
12
11
10
9
10 F
LOGIC
COMMON
39.2k
28.7k
316k
OUTPUT
OFFSET
NULL
R2
10k
+5V
TO –V
REV. E
V
1k
1k
1k
OUT