UM1036
Board description
Doc ID 18293 Rev 1
21/48
The op amp is used in follower mode with gain of the op amp set by resistors:
Equation 5
It is possible to calculate the voltage on the op amp output OP OUT - V
OUT
as the sum of
a bias
V
BIAS
and a signal
V
SIGN
component equal to:
Equation 6
Total gain of the circuit with the resistor divider is equal to:
Equation 7
With the default values this gives:
●
V
BIAS
= 0.38 V
●
Maximal voltage of V
SIGN
= 2.76 V
●
G = 8.02
●
G
TOT
= 6.90
●
Maximum current amplifiable without distortion is 16 A.
r
r1
R
L S
+
(
)
r
×
2
r1
R
LS
r2
+
+
----------------------------------------
=
G
R
r
+
r
------------
=
V
OU T
V
SIGN
V
BIAS
+
=
V
BI AS
3.3
1
R1
--------
1
R2
--------
1
R3
--------
+
+
⎝
⎠
⎛
⎞
R3
×
----------------------------------------------------------
G
×
=
V
SIGN
1
R
H S
×
1
R1
--------
1
R2
--------
1
R3
--------
+
+
⎝
⎠
⎛
⎞
R1
×
----------------------------------------------------------
G
×
=
G
TOT
V
SIGN
V
IN
----------------
V
SI GN
R
H S
I
×
--------------------
=
=
