Datasheet

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V
OCM
_
+
_
+
V
DD
V
IN-
V
IN+
V
O+
V
O-
Differential Structure Rejects
Coupled Noise at the Output
Differential Structure Rejects
Coupled Noise at the Input
Differential Structure Rejects
Coupled Noise at the Power Supply
GND
-
R
f
R
(g)
+
+
-
GND
V
DD
R
(g)
R
f
Vs
V
IN-
V
IN+
V
O+
V
O-
V
OCM
Note: For proper operation, maintain
symmetry by setting
R
f
1 = R
f
2 = R
f
and R
(g)
1 = R
(g)
2 = R
(g)
⇒ A = R
f
/R
(g)
-
R
f
R
(g)
+
+
-
GND
V
DD
R
(g)
R
f
Vs
V
IN-
V
IN+
V
O+
V
O-
V
OCM
GAIN R
(g)
Ω R
f
Ω
1 150 150
RECOMMENDED RESISTOR VALUES
V
O
+
1
2
V
I
(11)
V
O
+ –
1
2
V
I
(12)
THS4120
THS4121
SLOS319D – FEBRUARY 2001 – REVISED OCTOBER 2004
PRINCIPLES OF OPERATION (continued)
Figure 24. Definition of the Fully Differential Amplifier
The following schematics depict the differences between the operation of the THS412x, fully differential
amplifier, in two different modes. Fully differential amplifiers can work with differential input or can be
implemented as single in/differential out.
Figure 25. Amplifying Differential Signals
Figure 26. Single In With Differential Out
If each output is measured independently, each output is one-half of the input signal when gain is 1. The
following equations express the transfer function for each output:
The second output is equal and opposite in sign:
14
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