OPA682N BURR-BROWN [Burr-Brown Corporation], OPA682N Datasheet - Page 16

• Manufacturer Part Number: OPA682N
• Description: Wideband, Fixed Gain BUFFER AMPLIFIER With Disable
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

PRECISION VOLTAGE BUFFER
The precision buffer in Figure 6 combines the DC precision
and low 1/f noise of the OPA227 with the high speed
performance of the OPA682. The 80.6k
high frequency and low frequency nominal gains equal. The
OPA682 takes over from the OPA227 at approximately 32kHz.
FIGURE 6. Precision Wideband, Unity Gain Buffer.
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
Several PC boards are available to assist in the initial
evaluation of circuit performance using the OPA682 in its
three package styles. All of these are available free as an
unpopulated PC board delivered with descriptive documen-
tation. The summary information for these boards is shown
in the table below.
Contact the Burr-Brown applications support line to request
any of these boards.
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. A
SPICE model for the OPA682 is available through the Burr-
Brown Internet web page (http://www.burr-brown.com).
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 distortions, temperature or dG/d characteristics. These
models do not attempt to distinguish between the package
types in their small-signal AC performance.
PRODUCT
OPA682P
OPA682U
OPA682N
V
2.7nF
200
IN
2.7nF
OPA227
6-Lead SOT23-6
®
8-Lead SO-8
+5V
PACKAGE
8-Pin DIP
OPA682
–5V
80.6k
200
DEM-OPA68xP
DEM-OPA68xU
DEM-OPA68xN
400
NUMBER
BOARD
PART
OPA682
+5V
–5V
resistor makes the
400
LITERATURE
REQUEST
NUMBER
MKT-350
MKT-351
MKT-348
V
OUT
16
OPERATING SUGGESTIONS
GAIN SETTING
Setting the gain with the OPA682 is very easy. For a gain of
+2, ground the –IN pin and drive the +IN pin with the signal.
For a gain of +1, leave the –IN pin open and drive the +IN
pin with the signal. For a gain of –1, ground the +IN pin and
drive the –IN pin with the signal. Since the internal resistor
values (but not their ratio) change significantly over tem-
perature and process, external resistors should not be used to
modify the gain.
OUTPUT CURRENT AND VOLTAGE
The OPA682 provides output voltage and current capabili-
ties that are unsurpassed in a low cost monolithic op amp.
Under no-load conditions at 25 C, the output voltage typi-
cally swings closer than 1V to either supply rail; the guaran-
teed swing limit is within 1.2V of either rail. Into a 15 load
(the minimum tested load), it is guaranteed to deliver more
than 135mA.
The specifications described above, though familiar in the
industry, consider voltage and current limits separately. In
many applications, it is the voltage x current, or V-I product,
which is more relevant to circuit operation. Refer to the
“Output Voltage and Current Limitations” plot in the Typical
Performance Curves. The X and Y axes of this graph show
the zero-voltage output current limit and the zero-current
output voltage limit, respectively. The four quadrants give a
more detailed view of the OPA682’s output drive capabili-
ties, noting that the graph is bounded by a “Safe Operating
Area” of 1W maximum internal power dissipation. Superim-
posing resistor load lines onto the plot shows that the
OPA682 can drive
without exceeding the output capabilities or the 1W dissipa-
tion limit. A 100
shows the full 3.9V output swing capability, as shown in
the Typical Specifications.
The minimum specified output voltage and current over
temperature are set by worst-case simulations at the cold
temperature extreme. Only at cold startup will the output
current and voltage decrease to the numbers shown in the
guaranteed tables. As the output transistors deliver power,
their junction temperatures will increase, decreasing their
VBE’s (increasing the available output voltage swing) and
increasing their current gains (increasing the available out-
put current). In steady-state operation, the available output
voltage and current will always be greater than that shown in
the over-temperature specifications since the output stage
junction temperatures will be higher than the minimum
specified operating ambient.
To maintain maximum output stage linearity, no output
short-circuit protection is provided. This will not normally
be a problem since most applications include a series match-
ing resistor at the output that will limit the internal power
dissipation if the output side of this resistor is shorted to
ground. However, shorting the output pin directly to the
adjacent positive power supply pin will, in most cases,
destroy the amplifier. If additional short-circuit protection is
required, consider a small series resistor in the power supply
load line (the standard test circuit load)
2.5V into 25
or
3.5V into 50