Datasheet
Inside the INA19xA
R
S
A1
A2
R
L
Load
Negative
and Positive
Common-Mode
Voltage
V+
I
S
OUT =
I
S
R
S
R
L
INA193A–INA198A
5 kΩ 5 kΩ
5 kΩ
V
IN+
V
IN–
V
IN+
INA193A-Q1 , INA194A-Q1 , INA195A-Q1
INA196A-Q1 , INA197A-Q1 , INA198A-Q1
SBOS366C – AUGUST 2006 – REVISED OCTOBER 2008 ...............................................................................................................................................
www.ti.com
The INA19xA uses a new, unique, internal circuit topology that provides common-mode range extending from
– 16 V to +80 V while operating from a single power supply. The common-mode rejection in a classic
instrumentation amplifier approach is limited by the requirement for accurate resistor matching. By converting the
induced input voltage to a current, the INA19xA provides common-mode rejection that is no longer a function of
closely matched resistor values, providing the enhanced performance necessary for such a wide common-mode
range. A simplified diagram (see Figure 6 ) shows the basic circuit function. When the common-mode voltage is
positive, amplifier A2 is active.
The differential input voltage, V
IN+
– V
IN –
applied across R
S
, is converted to a current through a 5-k Ω resistor.
This current is converted back to a voltage through R
L
, and then amplified by the output buffer amplifier. When
the common-mode voltage is negative, amplifier A1 is active. The differential input voltage, V
IN+
– V
IN –
applied
across R
S
, is converted to a current through a 5-k Ω resistor. This current is sourced from a precision current
mirror whose output is directed into R
L
, converting the signal back into a voltage and amplified by the output
buffer amplifier. Patent-pending circuit architecture ensures smooth device operation, even during the transition
period where both amplifiers A1 and A2 are active.
Figure 6. INA19xA Simplified Circuit Diagram
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Product Folder Link(s): INA193A-Q1 INA194A-Q1 INA195A-Q1 INA196A-Q1 INA197A-Q1 INA198A-Q1