OPA641H BURR-BROWN [Burr-Brown Corporation], OPA641H Datasheet - Page 8

• Manufacturer Part Number: OPA641H
• Description: Wideband Voltage Feedback OPERATIONAL AMPLIFIER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

the end of the datasheet. A longer feedback path than this
will decrease the realized bandwidth substantially.
6) Due to the extremely high bandwidth of the OPA641, the
SOIC package is strongly recommended due its low para-
sitic impedance. The parasitic impedance in the PDIP and
CERDIP packages causes the OPA641 to experience about
5dB of gain peaking in unity-gain configurations. This is
compared with virtually no gain peaking in the SOIC pack-
age in unity-gain. The gain peaking in the PDIP and CERDIP
packages is minimized in gains of 4 or greater, however.
Surface mount components (chip resistors, capacitors, etc.)
also have low lead inductance and are therefore strongly
recommended.
7) Avoid overloading the output. Remember that output
current must be provided by the amplifier to drive its own
feedback network as well as to drive its load. Lowest
distortion is achieved with high impedance loads.
8) Don’t forget that these amplifiers use
Although they will operate perfectly well with +5V and
–5.2V, use of 15V supplies will destroy the part.
9) Standard commercial test equipment has not been de-
signed to test devices in the OPA641’s speed range. Bench-
top op amp testers and ATE systems will require a special
test head to successfully test these amplifiers.
10) Terminate transmission line loads. Unterminated lines,
such as coaxial cable, can appear to the amplifier to be a
capacitive or inductive load. By terminating a transmission
line with its characteristic impedance, the amplifier’s load
then appears purely resistive.
11) Plug-in prototype boards and wire-wrap boards will not
be satisfactory. A clean layout using RF techniques is
essential; there are no shortcuts.
OFFSET VOLTAGE ADJUSTMENT
If additional offset adjustment is needed, the circuit in
Figure 1 can be used without degrading offset drift with
temperature. Avoid external adjustment whenever possible
FIGURE 1. Offset Voltage Trim.
NOTE: (1) R
bias currents.
20k
+V
–V
3
CC
CC
is optional and can be used to cancel offset errors due to input
Output Trim Range
®
OPA641
10µF
R
47k
Trim
R
1
V
IN
+V
or Ground
CC
R
R
Trim
2
R
OPA641
to –V
3
(1)
R
= R
2
CC
1
5V supplies.
|| R
R
R
Trim
2
2
8
since extraneous noise, such as power supply noise, can be
inadvertently coupled into the amplifier’s inverting input
terminal. Remember that additional offset errors can be
created by the amplifier’s input bias currents. Whenever
possible, match the impedance seen by both inputs as is
shown with R
the amplifier’s offset current.
INPUT PROTECTION
Static damage has been well recognized for MOSFET de-
vices, but any semiconductor device deserves protection
from this potentially damaging source. The OPA641 incor-
porates on-chip ESD protection diodes as shown in Figure 2.
This eliminates the need for the user to add external protec-
tion diodes, which can add capacitance and degrade AC
performance.
All pins on the OPA641 are internally protected from ESD
FIGURE 2. Internal ESD Protection.
by means of a pair of back-to-back reverse-biased diodes to
either power supply as shown. These diodes will begin to
conduct when the input voltage exceeds either power supply
by about 0.7V. This situation can occur with loss of the
amplifier’s power supplies while a signal source is still
present. The diodes can typically withstand a continuous
current of 30mA without destruction. To insure long term
reliability, however, diode current should be externally lim-
ited to 10mA or so whenever possible.
The OPA641 utilizes a fine geometry high speed process
that withstands 500V using Human Body Model and 100V
using the Machine Model. However, static damage can
cause subtle changes in amplifier input characteristics with-
out necessarily destroying the device. In precision opera-
tional amplifiers, this may cause a noticeable degradation of
offset voltage and drift. Therefore, static protection is strongly
recommended when handling the OPA641.
OUTPUT DRIVE CAPABILITY
The OPA641 has been optimized to drive 75
resistive loads. The device can drive 2Vp-p into a 75 load.
This high-output drive capability makes the OPA641 an
ideal choice for a wide range of RF, IF, and video applica-
tions. In many cases, additional buffer amplifiers are un-
needed.
External
Pin
3.
This will reduce input bias current errors to
+V
–V
CC
CC
ESD Protection diodes internally
connected to all pins.
Internal
Circuitry
and 100