Datasheet

75W
+5V
-5V
OPA4872
75W
75W
75W
75W
To75 LoadW
523W
523W
IN0
IN1
IN2
IN3
V
IN0
V
IN1
V
IN2
V
IN3
A0
A1
SD
EN
V
OUT
0.1 Fm
Optional
0.01 Fm
6.8 Fm
+
0.1 Fm 6.8 Fm
+
OPA4872
SBOS346C –JUNE 2007–REVISED MARCH 2011 www.ti.com
APPLICATION INFORMATION
input of a current feedback amplifier. Depending on
the logic applied to channel control pins A0 and A1,
WIDEBAND MULTIPLEXER OPERATION
one switch is on at all times. Figure 27 represents the
The OPA4872 gives a new level of performance in
OPA4872 in this configuration. The truth table for
wideband multiplexers. Figure 27 shows the
channel selection is shown in Table 2.
dc-coupled, gain of +2V/V, dual power-supply circuit
used as the basis of the ±5V Electrical
Table 2. TRUTH TABLE
Characteristics and Typical Characteristic curves. For
A0 A1 EN SD V
OUT
test purposes, the input impedance is set to 75Ω with
0 0 0 0 IN0
a resistor to ground and the output impedance is set
to 75Ω with a series output resistor. Voltage swings
1 0 0 0 IN1
reported in the specifications are taken directly at the
0 1 0 0 IN2
input and output pins while load powers (in dBm) are
1 1 0 0 IN3
defined at a matched 75Ω load. For the circuit of
X X 1 0 High-Z, I
Q
= 3.4mA
Figure 27, the total effective load will be 150Ω ||
X X X 1 High-Z, I
Q
= 1.1mA
1046Ω = 131Ω. Logic pins A0 and A1 control which
of the four inputs is selected while EN and SD allow
The OPA4872 is in disable mode, with a quiescent
for power reduction. One optional component is
current of 3.4mA typical, when the EN pin is set to
included in Figure 27. In addition to the usual
0V. After being placed in disable mode, the OPA4872
power-supply decoupling capacitors to ground, a
is fully enabled in 6ns. For further power savings, the
0.01μF capacitor is included between the two
SD pin can be used. Setting the SD pin to 5V places
power-supply pins. In practical printed circuit board
the device in shutdown mode with a standing
(PCB) layouts, this optional added capacitor typically
quiescent current of 1.1mA. Note that in this
improves the 2nd-harmonic distortion performance by
shutdown mode, the OPA4872 requires 15ns to be
3dB to 6dB for bipolar supply operation.
fully powered again. The truth table for disable and
Even though the internal architecture of the OPA4872
shutdown modes can be found in Table 2.
includes current steering, it is advantageous to look
at it as four switches looking into the noninverting
Figure 27. DC-Coupled, G = +2V/V Bipolar Specification and Test Circuit (Channel 0 Selected)
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