OPA642N BURR-BROWN [Burr-Brown Corporation], OPA642N Datasheet - Page 15

• Manufacturer Part Number: OPA642N
• Description: Wideband, Low Distortion, Low Gain OPERATIONAL AMPLIFIER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

e) Socketing a high speed part like the OPA642 is not
INPUT AND ESD PROTECTION
The OPA642 is built using a very high speed complemen-
tary bipolar process. The internal junction breakdown volt-
ages are relatively low due to these very small geometry
devices. These breakdowns are reflected in the Absolute
Maximum Rating table. All device pins are protected with
internal ESD protection diodes to the power supplies as
shown in Figure 9.
FIGURE 9. Internal ESD Protection.
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 15V supply parts
driving into the OPA642), 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.
High input overdrive signals can also cause significant
differential voltage between the + and – inputs. Where this
voltage can exceed the maximum rated voltage of 1.2V,
external Schottky protection diodes should be added across
the two inputs. Again, the capacitance added by these diodes
can degrade the noise and AC performance and should be
used only where necessary. Figure 9 shows a fully featured
input protection circuit for the OPA642. This is the circuit of
Figure 1 with additional limiting resistors into the inputs and
Schottky clamp diodes across the inputs. These resistor
values have been selected to limit the degradation in noise
and frequency response, achieve DC bias current cancella-
tion, and limit the current that will flow under overdrive
conditions.
recommended. The additional lead length and pin-to-pin
capacitance introduced by the socket can create an ex-
tremely troublesome parasitic network which can make it
almost impossible to achieve a smooth, stable frequency
response. Best results are obtained by soldering the
OPA642 onto the board. If socketing for the DIP package
is desired, high frequency flush mount pins (e.g.,
McKenzie Technology #710C) can give good results.
External
Pin
+V
–V
CC
CC
Internal
Circuitry
15
FIGURE 10. Gain of +2 with Input Protection.
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
Several PC boards are available in the initial evaluation of
circuit performance using the OPA642 in its three package
styles. Two partially assembled boards are available for sale
to support the DIP (P suffix) and SO-8 (U-suffix) packages.
These boards come partially assembled with power supply
and I/O connectors but do not have the amplifier or resistor
networks loaded. Both boards are configured for low
distortion, non-inverting amplifier operation. Order these
boards by the following part numbers from your local Burr-
Brown distributor:
DEM-OPA64XP-N for the OPA642P and OPA642PB (8-pin DIP package)
DEM-OPA64XU-N for the OPA642U and OPA642UB (8-pin SO package)
The SOT23-5 package version of the OPA642 may be
evaluated using a single unpopulated board used for numerous
SOT23-5 packaged amplifiers available from Burr-Brown.
This board is available from the Burr-Brown Literature
department as an unpopulated board attached to a descriptive
document. This board, the DEM-OPA6xxN, is available
free by requesting literature number MKT-348.
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 OPA642 is available through either the
Burr-Brown web page (http://www.burr-brown.com) or as a
disk from the Burr-Brown Applications Department (1-800-
548-6132). The application department is also available for
design assistance at this number. 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 good a job in predicting the harmonic distortion or dG/dP
characteristics. These models do not attempt to distinguish
between the package types in their small signal AC perfor-
mance.
50 Source
50
174
D1
50
301
D2
OPA642
D1, D2
OPA642
+5V
–5V
301
Decoupling Not Shown
IN5911 (or equivalent)
Power Supply
50
®