Datasheet

+Vs
+Vs
-Vs
-Vs
+Vs
-Vs
Vout
-
+
+
U2 OPA170
R1 10k
R2 10k
C1 100p
Rset 10k
RG 1k
+
Vin
A
+
Iset
RL 1k
-
+
Vdiff
+
+
-
Rg
Rg
Ref
U4 INA826
V1 15
V2 15
INA826
SBOS562E –AUGUST 2011–REVISED APRIL 2013 www.ti.com
The circuit in Figure 70 creates a precision current I
SET
by forcing the INA826 V
DIFF
across R
SET
. The input
voltage V
IN
is amplified to the output of the INA826 and then divided down by the gain of the INA826 to create
V
DIFF
. I
SET
can be controlled either by changing the value of the gain-set resistor R
G
, the set resistor R
SET
, or by
changing V
OUT
through the gain of the composite loop. Care must be taken to ensure that the changing load
resistance R
L
does not create a voltage on the negative input of the INA826 that violates the compliance of the
common-mode input range. Likewise, the voltage on the output of the OPA170 must remain compliant
throughout the changing load resistance for this circuit to work properly. Click the following link to download the
TINA-TI file: Current Source.
Figure 70. Precision Current Source
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Product Folder Links: INA826