OPA2652 Datasheet, PDF (9/15 Pages) Burr-Brown (TI) – Dual, 700MHz, Voltage-Feedback OPERATIONAL AMPLIFIER

APPLICATIONS INFORMATION
WIDEBAND VOLTAGE FEEDBACK OPERATION
The OPA2652 is a dual low power, wideband voltage
feedback operational amplifier. Each channel is internally
compensated to provide unity gain stability. The OPA2652’s
voltage feedback architecture features true differential and
fully symmetrical inputs. This minimizes offset errors, mak-
ing the OPA2652 well suited for implementing filter and
instrumentation designs. As a dual operational amplifier,
OPA2652 is an ideal choice for designs requiring multiple
channels where reduction of board space, power dissipation
and cost are critical. Its AC performance is optimized to
provide a gain bandwidth product of 200MHz and a fast rise
time of 2.0ns, which is an important consideration in high
speed data conversion applications. The low DC input offset
of ±1.5mV and drift of ±5µV/°C support high accuracy
requirements. In applications requiring a higher slew rate
and wider bandwidth, such as video and high bit rate digital
communications, consider the dual current feedback
OPA2658, or OPA2681.
Figure 1 shows the DC-coupled, gain of +2, dual power
supply circuit configuration used as the basis of the ±5V
Specifications and Typical Performance Curves. This is for
one channel. The other channel is connected similarly. For
test purposes, the input impedance is set to 50Ω with a
resistor to ground and the output impedance is set to 50Ω
with a series output resistor. Voltage swings reported in the
specifications are taken directly at the input and output pins,
while output powers (dBm) are at the matched 50Ω load. For
the circuit of Figure 1, the total effective load will be 100Ω
|| 804Ω. Two optional components are included in Figure 1.
+5V
0.1µF
6.8µF
+
50Ω Source
174Ω
V_I
49.9Ω
1/2
OPA2652
50Ω Load
V_O 49.9Ω
0.1µF
R_G
402Ω
R_F
402Ω
6.8µF
–5V
0.1µF
FIGURE 1. DC-Coupled, G = +2, Bipolar Supply, Specifi-
cation and Test Circuit.
An additional resistor (174Ω) is included in series with the
non-inverting input. Combined with the 25Ω DC source
resistance looking back towards the signal generator, this
gives an input bias current cancelling resistance that matches
the 201Ω source resistance seen at the inverting input (see the
DC Accuracy and Offset Control section). In addition to the
usual power supply decoupling capacitors to ground, a 0.1µF
capacitor is included between the two power supply pins. In
practical PC board layouts, this optional-added capacitor will
typically improve the 2nd harmonic distortion performance
by 3dB to 6dB.
Figure 2 shows the DC-coupled gain of –1, bipolar supply
circuit configuration which is the basis of the Specifications
and Typical Performance Curves at G = –1. The input
impedance matching resistor (57.6Ω) used for testing gives a
50Ω input load. A resistor (205Ω) connects the non-inverting
input to ground. This provides the DC source resistance
matching to cancel outputs errors due to input bias current.
+5V
0.1µF
R_B
205Ω
+
0.1µF
6.8µF
1/2
OPA2652
R_O
V_O 49.9Ω
50Ω Load
50Ω
Source
V_I
R_G
402Ω
R_M
57.6Ω
R_F
402Ω
V_O
V_I
= –1
0.1µF
6.8µF
+
–5V
FIGURE 2. DC-Coupled, G = –1, Bipolar Supply, Specifi-
cation and Test Circuit.
DIFFERENTIAL ADC DRIVER
The circuit on the front page shows an OPA2652 driving the
ADS807 A/D converter differentially, at a gain of +2V/V.
The outputs are AC-coupled to the converter to adjust for the
difference in supply voltages. The 133Ω resistors at the non-
inverting inputs minimize DC offset errors. The differential
topology minimizes even-order distortion products, such as
second-harmonic distortion.
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OPA2652