OPA2652 Datasheet, PDF (11/15 Pages) Burr-Brown (TI) – Dual, 700MHz, Voltage-Feedback OPERATIONAL AMPLIFIER

C
V_IN
R
+5V
1/2
OPA2652
R_G
402Ω
–5V
R_F
402Ω
+5V
C
1/2
OPA2652
V_O
R
402Ω
–5V
402Ω
FIGURE 6. Pulse Delay Circuit.
R_F and R_G need to be equal to maintain a constant gain
magnitude. The rise and fall times of the input pulses (t_r(IN) )
should be slow enough to prevent pre-shoot artifacts in the
response.
t_r(IN) ≥ 5RC, minimal pre-shoot
SIMPLE BANDPASS FILTER
Figure 7 shows the OPA2652 used as simple bandpass filter.
The OPA2652 is well suited for this type of circuit because
it is very stable at a noise gain of +1.
C₂
MACROMODELS AND APPLICATIONS SUPPORT
Computer simulation of circuit performance using SPICE is
often useful when analyzing the performance of analog
circuits and systems. This is particularly true for Video and
RF amplifier circuits where parasitic capacitance and induc-
tance can have a major effect on circuit performance. Check
the Burr-Brown web site (www.burr-brown.com) for avail-
able SPICE products (not all parts have models). These
models do a good job of predicting small-signal AC and
transient performance under a wide variety of operating
conditions. They do not do as well in predicting the har-
monic distortion or dG/dφ characteristics. These models do
not attempt to distinguish between the package types in their
small-signal AC performance.
C_{1 402Ω}
V_IN
402Ω
+5V
V_OUT
OPERATING SUGGESTIONS
OPTIMIZING RESISTOR VALUES
Since the OPA2652 is a unity gain stable voltage feedback
op amp, a wide range of resistor values may be used for the
1/2
OPA2652
feedback and gain setting resistors. The primary limits on
these values are set by dynamic range (noise and distortion)
and parasitic capacitance considerations. For a non-inverting
402Ω
–5V
unity gain follower application, the feedback connection
should be made with a 25Ω resistor, not a direct short. This
will isolate the inverting input capacitance from the output
pin and improve the frequency response flatness. Usually,
FIGURE 7. Inverting Bandpass Filter.
the feedback resistor value should be between 200Ω and
1.5kΩ. Below 200Ω, the feedback network will present
DESIGN-IN TOOLS
additional output loading which can degrade the harmonic
distortion performance of the OPA2652. Above 1.5kΩ, the
DEMONSTRATION BOARDS
PC boards are available to assist in the initial evaluation of
circuit performance using the OPA2652. They are available
free as unpopulated PC boards delivered with descriptive
documentation. The summary information for these boards is
shown below:
typical parasitic capacitance (approximately 0.2pF) across
the feedback resistor may cause unintentional band-limiting
in the amplifier response.
A good rule of thumb is to target the parallel combination of
R_F and R_G (Figure 1) to be less than approximately 300Ω.
The combined impedance R_F || R_G interacts with the invert-
ing input capacitance, placing an additional pole in the
feedback network, and thus a zero in the forward response.
PRODUCT
OPA2652U
OPA2652E
PACKAGE
8-Lead SO-8
SOT23-8
BOARD
PART
NUMBER
DEM-OPA26xU
DEM-OPA2652E
ORDERING
NUMBER
MKT-352
MKT-365
Contact the Burr-Brown Applications support line to request
this board.
Assuming a 2pF total parasitic on the inverting node, hold-
ing R_F || R_G < 300Ω will keep this pole above 250MHz. By
itself, this constraint implies that the feedback resistor R_F
can increase to several kΩ at high gains. This is acceptable
as long as the pole formed by R_F and any parasitic capaci-
tance appearing in parallel is kept out of the frequency range
of interest.
®
11
OPA2652