AD620B AD [Analog Devices], AD620B Datasheet - Page 15

• Manufacturer Part Number: AD620B
• Description: Low Cost, Low Power Instrumentation Amplifier
• Manufacturer: AD [Analog Devices]

GROUND RETURNS FOR INPUT BIAS CURRENTS
Input bias currents are those currents necessary to bias the input
transistors of an amplifier. There must be a direct return path
for these currents; therefore, when amplifying “floating” input
REV. E
Figure 42a. Ground Returns for Bias Currents with
Transformer Coupled Inputs
+ INPUT
– INPUT
R
G
Figure 42c. Ground Returns for Bias Currents with AC Coupled Inputs
AD620
–V
+V
S
S
REFERENCE
100k
100k
LOAD
– INPUT
+ INPUT
TO POWER
GROUND
SUPPLY
R
G
V
OUT
AD620
–15–
–V
+V
sources such as transformers, or ac-coupled sources, there must
be a dc path from each input to ground as shown in Figure 42.
Refer to the Instrumentation Amplifier Application Guide (free
from Analog Devices) for more information regarding in amp
applications.
S
S
Figure 42b. Ground Returns for Bias Currents with
Thermocouple Inputs
REFERENCE
+ INPUT
– INPUT
LOAD
TO POWER
R
GROUND
G
SUPPLY
V
OUT
AD620
+V
–V
S
S
REFERENCE
AD620
LOAD
TO POWER
GROUND
SUPPLY
V
OUT