Datasheet

V =
OUT+
V (1 ) V (1 )+2V b
IN+ IN OCM-
- b - - b
2b
(1)
V =
OUT-
- bV (1 )+V (1 )+2V
IN+ IN OCM-
- b - b
2b
(2)
V =V (1 )+V- b
N IN OUT+-
b
(3)
V
OCM
+V
S
V
S
R
S
R
G1
R
G2
R
F1
R
F2
+
R
T
+
-
-
b =
R
G
R +R
F G
(4)
V =V (1 )+V- b
P IN+ OUT-
b
(5)
V
OCM
+V
S
V
S
R
S
R
G1
R
G2
R
F1
R
F2
+
R
T
+
-V
S
-
-
V
OCM
R
G
R
G
R
F
R
F
+
+
V
P
V
N
V
OUT-
V
OUT+
V
IN+
V
IN-
-
-
THS4504
THS4505
SLOS363D – AUGUST 2002 – REVISED MAY 2008 ......................................................................................................................................................... www.ti.com
Where:
Figure 76. Application Circuit for the THS4500 and
THS4501, Featuring Single-Supply Operation with
a Ground-Referenced Input Signal
NOTE:
The equations denote the
device inputs as V
N
and
V
P
, and the circuit inputs
as V
IN+
and V
IN –
.
Figure 77. Application Circuit for the THS4500 and
THS4501, Featuring Split-Supply Operation with
an Input Signal Referenced at the Midrail
Equation 1 to Equation 5 allow calculation of the
Figure 78. Diagram for Input Common-Mode
required input common-mode range for a given set of
Range Equations
input conditions.
The equations allow calculation of the input common-
Table 1 and Table 2 show the input common-mode
mode range requirements given information about the
range requirements for two different input scenarios,
input signal, the output voltage swing, the gain, and
an input referenced around the negative rail and an
the output common-mode voltage. Calculating the
input referenced around midrail. The tables highlight
maximum and minimum voltage required for V
N
and
the differing requirements on input common-mode
V
P
(the amplifier input nodes) determines whether or
range, and illustrate reasoning for choosing either the
not the input common-mode range is violated or not.
THS4500/1 or the THS4502/3. For signals referenced
Four equations are required. Two calculate the output
around the negative power supply, the THS4500/1
voltages and two calculate the node voltages at V
N
should be chosen since its input common-mode
and V
P
(note that only one of these needs calculation,
range includes the negative supply rail. For all other
as the amplifier forces a virtual short between the two
situations, the THS4502/3 offers slightly improved
nodes).
distortion and noise performance for applications with
input signals centered between the power-supply
rails.
Table 1. Negative-Rail Referenced
Gain (V/V) V
IN+
(V) V
IN –
(V) V
IN
(V
PP
) V
OCM
(V) V
OD
(V
PP
) V
NMIN
(V) V
NMAX
(V)
1 – 2.0 to 2.0 0 4 2.5 4 0.75 1.75
2 – 1.0 to 1.0 0 2 2.5 4 0.5 1.167
4 – 0.5 to 0.5 0 1 2.5 4 0.3 0.7
8 – 0.25 to 0.25 0 0.5 2.5 4 0.167 0.389
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