OPA2607 Datasheet, PDF (11/13 Pages) Burr-Brown (TI) – Dual, High Output, Current-Feedback OPERATIONAL AMPLIFIER

connections (on pins 4 and 7) should always be decoupled
with these capacitors. An optional supply decoupling ca-
pacitor across the two power supplies (for bipolar operation)
will improve 2nd harmonic distortion performance. Larger
(2.2µF to 6.8µF) decoupling capacitors, effective at lower
frequency, should also be used on the main supply pins.
These may be placed somewhat farther from the device and
may be shared among several devices in the same area of the
PC board.
c) Careful selection and placement of external compo-
nents will preserve the high-frequency performance of
the OPA2607. Resistors should be a very low reactance
type. Surface-mount resistors work best and allow a tighter
overall layout. Metal film and carbon composition axially
leaded resistors can also provide good high-frequency per-
formance. Again, keep their leads and PC board trace length
as short as possible. Never use wirewound-type resistors in
a high-frequency application. Since the output pin and in-
verting input pin are the most sensitive to parasitic capaci-
tance, always position the feedback and series output resis-
tor, if any, as close as possible to the output pin. Other
network components, such as non-inverting input termina-
tion resistors, should also be placed close to the package.
Where double-side component mounting is allowed, place
the feedback resistor directly under the package on the other
side of the board between the output and inverting input
pins. The frequency response is primarily determined by the
feedback resistor value as described previously. Increasing
its value will reduce the bandwidth, while decreasing it will
give a more peaked frequency response. The 1.21kΩ feed-
back resistor used in the typical performance specifications
at a gain of +8 on ±12V supplies is a good starting point for
design. Note that a 1.50kΩ feedback resistor, rather than a
direct short, is recommended for the unity-gain follower
application. A current-feedback op amp requires a feedback
resistor even in the unity-gain follower configuration to
control stability.
d) Connections to other wideband devices on the board
may be made with short direct traces or through on-board
transmission lines. For short connections, consider the trace
and the input to the next device as a lumped capacitive load.
Relatively wide traces (50 to 100mils) should be used,
preferably with ground and power planes opened up around
them. Estimate the total capacitive load and set R_S from the
plot of recommended “R_S vs Capacitive Load”. Low para-
sitic capacitive loads (< 5pF) may not need an R_S since the
OPA2607 is nominally compensated to operate with a 2pF
parasitic load. If a long trace is required, and the 6dB signal
loss intrinsic to a doubly-terminated transmission line is
acceptable, implement a matched-impedance transmission
line using microstrip or stripline techniques (consult an ECL
design handbook for microstrip and stripline layout tech-
niques). A 50Ω environment is normally not necessary on
board, and in fact a higher-impedance environment will
improve distortion as shown in the “Distortion vs Load”
plots. With a characteristic board-trace impedance defined
based on board material and trace dimensions, a matching
series resistor into the trace from the output of the OPA2607
is used as well as a terminating shunt resistor at the input of
the destination device. Remember also that the terminating
impedance will be the parallel combination of the shunt
resistor and the input impedance of the destination device:
this total effective impedance should be set to match the
trace impedance. The high output voltage and current capa-
bility of the OPA2607 allows multiple destination devices to
be handled as separate transmission lines, each with their
own series and shunt terminations. If the 6dB attenuation of
a doubly-terminated transmission line is unacceptable, a
long trace can be series-terminated at the source end only.
Treat the trace as a capacitive load in this case and set the
series resistor value as shown in the plot of “R_S vs Capaci-
tive Load”. This will not preserve signal integrity as well as
a doubly-terminated line. If the input impedance of the
destination device is low, there will be some signal attenu-
ation due to the voltage divider formed by the series output
into the terminating impedance.
e) Do not socket a high speed part like the OPA2607. The
additional lead length and pin-to-pin capacitance introduced
by the socket can create an extremely troublesome parasitic
network which can make it almost impossible to achieve a
smooth, stable frequency response. Best results are obtained
by soldering the OPA2607 onto the board.
f) Use the –V_S plane to conduct heat out of the PSO-8 and
PSO-14 Power Packages (OPA2607H and OPA2607N).
These packages attach the die directly to a metal slug in its
bottom, which you should solder to the board. This slug
needs to be connected electrically to the negative supply
plane, which must have a minimum area of 2" x 2" (50mm
x 50mm) to produce the θ_JA values in the specifications
table. More details will be found in the data sheets that
accompany the demo boards described in the Demonstration
Boards section of this data sheet.
INPUT AND ESD PROTECTION
The OPA2607 is built using a very high-speed complemen-
tary bipolar process. All device pins have ESD protection
using internal diodes to the power supplies as shown in
Figure 6. The OPA2607 has an ESD rating of 4000V human
body model, and 300V machine model.
These diodes provide moderate protection to input overdrive
voltages above the supplies as well. The protection diodes
can typically support 30mA continuous current. Where higher
currents are possible (e.g. in systems with ±30V supply parts
driving into the OPA2607), current-limiting series resistors
should be added into the two inputs. Keep these resistor
values as low as possible since high values degrade both
noise performance and frequency response.
+V_CC
External
Pin
–V _CC
FIGURE 6. Internal ESD Protection.
Internal
Circuitry
®
11
OPA2607