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APPLICATIONS INFORMATION
Wideband Voltage Feedback Operation
V
O
V
I
1/2
OPA2652
50W
R
F
402W
R
G
402W
R
B
205W
R
M
57.6W
Source
+5V
-5V
R
O
49.9W
0.1 Fm 6.8 Fm
+
0.1 Fm
0.1 Fm
6.8 Fm
+
50 LoadW
= 1-
V
O
V
I
1/2
OPA2652
+5V
+
-5V
50 LoadW
49.9W
174W
49.9WV
O
V
I
50 SourceW
R
G
402W
R
F
402W
+
6.8 Fm
0.1 Fm 6.8 Fm
0.1 Fm
0.1 Fm
OPA2652
SBOS125A – JUNE 2000 – REVISED MAY 2006
Voltage swings reported in the specifications are
taken directly at the input and output pins, while
The OPA2652 is a dual, low-power, wideband
output powers (dBm) are at the matched 50 Ω load.
voltage feedback operational amplifier. Each channel
For the circuit of Figure 28 , the total effective load
is internally compensated to provide unity gain
will be 100 Ω || 804 Ω . Two optional components are
stability. The OPA2652 voltage feedback architecture
included in Figure 28 .
features true differential and fully symmetrical inputs.
This architecture minimizes offset errors, making the
An additional resistor (174 Ω ) is included in series
OPA2652 well-suited for implementing filter and
with the noninverting input. Combined with the 25 Ω
instrumentation designs. As a dual operational
DC source resistance looking back towards the
amplifier, OPA2652 is an ideal choice for designs
signal generator, this additional resistor gives an
that require multiple channels where reduction of
input bias current cancelling resistance that matches
board space, power dissipation and cost are critical.
the 201 Ω source resistance seen at the inverting
Its AC performance is optimized to provide a gain
input (see the DC Accuracy and Offset Control
bandwidth product of 200MHz and a fast rise time of
section). In addition to the usual power-supply
2.0ns, which is an important consideration in
decoupling capacitors to ground, a 0.1 µ F capacitor is
high-speed data conversion applications. The low
included between the two power-supply pins. In
DC input offset of ± 1.5mV and drift of ± 5 µ V/ ° C
practical printed circuit board (PCB) layouts, this
support high accuracy requirements. In applications
optional-added capacitor typically improves the
requiring a higher slew rate and wider bandwidth,
2nd-harmonic distortion performance by 3dB to 6dB.
such as video and high bit rate digital
Figure 29 shows the DC-coupled, gain of –1, bipolar
communications, consider the dual current feedback
supply circuit configuration that is the basis of the
OPA2694, or the OPA2691.
specifications and typical characteristics at G = –1.
Figure 28 shows the DC-coupled, gain of +2, dual
The input impedance matching resistor (57.6 Ω ) used
power-supply circuit configuration used as the basis
for testing gives a 50 Ω input load. A resistor (205 Ω )
of the ± 5V specifications and typical characteristics.
connects the noninverting input to ground. This
This configuration is for one channel. The other
configuration provides the DC source resistance
channel is connected similarly. For test purposes, the
matching to cancel outputs errors arising from input
input impedance is set to 50 Ω with a resistor to
bias current.
ground and the output impedance is set to 50 Ω with
a series output resistor.
Figure 29. DC-Coupled, G = –1, Bipolar Supply,
Specification and Test Circuit
Figure 28. DC-Coupled, G = +2, Bipolar Supply,
Specification and Test Circuit
10
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