R4 may be optionally populated with a resistor equivalent
to R
G
||R
FB
for increased precision over temperature. R4
will cancel out I
B
and potential parasitic thermocouples
at the inputs.
NON-INVERTING GAIN
A
V
=
1 + R
FB
R
G
To set the board up for non-inverting gain with split sup-
plies (see Figure 5):
1. Populate R5 with the desired R
FB
2. Populate R2 with the desired R
G
3. Tie –IN turret to GND (or populate Z3 with 0Ω)
4. Connect the input signal to the +IN turret
ADDING DC BIASES
To add a DC bias using a resistor divider, populate Z1 and
R9/R10 with the same value resistor to set the same DC
offset at both inputs. To keep total power consumption in
the microwatts, choose R
G
and R
FB
values in the 100’s of
kilohm to single-digit megohm range.
The circuit in Figure 6 level shifts an input signal’s com-
mon mode voltage from 0V to mid-rail (V
+
/2), with invert-
ing gain of –R
FB
/R
G
. The DC bias added to –IN is set by
divider Z1 and R1, and the DC bias added to +IN is set by
divider R9 and R3.
Figure 5. Non-Inverting Gain
R4 may be optionally populated with a resistor equivalent
to R
G
||R
FB
for increased precision over temperature. R4
will cancel out I
B
and potential parasitic thermocouples
at the inputs.
OUT
1
3
–IN
+IN
J1
C10
0.1µF
R1
0Ω
R3
0Ω
R2
R
G
R4*
R
G
||R
FB
R6
0Ω
R7
49.9Ω
R8
1k
R5
R
FB
V
+
2
V
–
ENABLED
*OPTIONAL
V
+
V
–
DC2837A-B F05
S
Figure 6. Inverting Gain with DC Bias
OUT
–IN
+IN
R1
R
G
R3
R
G
R2
0Ω
R4
0Ω
R6
0Ω
R7
49.9Ω
R5
R
FB
Z5
0Ω
JP3
R9
R
G
JP2
Z1
R
G
JP1
R10
0Ω
V
+
ENABLED (JP6 TIED TO V
+
)
V
+
V
+
V
–
V
–
V
CM
= 0
V
+
V
CM
= V
+
/2
DC2837A-B F06
S
To build the Figure 6 level shift circuit with DC2837A:
1. Remove default R1 – R5 and R9
2. Stuff R1, R3, R9, and Z1 with desired R
G
3. Stuff R2, R4, Z5 with 0Ω
4. Stuff R5 with desired R
FB
5. Tie +IN turret to GND (or populate Z4 with 0Ω)
6. Jumper settings: JP1 to 1 (V
+
), JP3 to 1 (R9),
JP2 installed
7. Connect the –IN turret to input signal
5
DEMO MANUAL
Rev. 0
OPERATING PRINCIPLES
