ad841sq-883b Analog Devices, Inc., ad841sq-883b Datasheet - Page 8

• Manufacturer Part Number: ad841sq-883b
• Description: Wideband, Unity-gain Stable, Fast Settling Op Amp
• Manufacturer: Analog Devices, Inc.

AD841
USING A HEAT SINK
The AD841 draws less quiescent power than most precision
high speed amplifiers and is specified for operation without a
heat sink. However, when driving low impedance loads, the cur-
rent to the load can be 4 to 5 times the quiescent current. This
will create a noticeable temperature rise. Improved performance
can be achieved by using a small heat sink such as the Aavid
Engineering #602B.
TERMINATED LINE DRIVER
The AD841 functions very well as a high speed line driver of ei-
ther terminated or unterminated cables. Figure 26 shows the
AD841 driving a doubly terminated cable in a follower configu-
ration. The AD841 maintains a typical slew rate of 300 V/ s,
impedance of the cable) minimizes reflections from the far end
of the cable. A back-termination resistor (R
characteristic impedance of the cable) may be placed between
the AD841 output and the cable in order to damp any stray sig-
nals caused by a mismatch between R
teristic impedance. This will result in a “cleaner” signal, but
since 1/2 the output voltage will be dropped across R
amp must supply double the output signal required if there is no
back termination. Therefore the full power bandwidth is cut in
half.
If termination is not used, cables appear as capacitive loads. If
this capacitive load is large, it should be decoupled from the
AD841 by a resistor in series with the output (see above:
Driving a Capacitive Load).
OVERDRIVE RECOVERY
Figure 27 shows the overdrive recovery capability of the AD841.
Typical recovery time is 200 ns from negative overdrive and
700 ns from positive overdrive.
which means it can drive a 10 V, 4.7 MHz signal or a 3 V,
15.9 MHz signal.
The termination resistor, R
Figure 25. Circuit for Driving a Large Capacitive Load
Figure 26. Line Driver Configuration
T
, (when equal to the characteristic
T
and the cable’s charac-
BT
, also equal to the
BT
, the op
–8–
14-Pin Plastic (N) Package
12-Lead Metal Can Package
Figure 28. Overdrive Recovery Test Circuit
(TO-8 Style)
Figure 27. Overdrive Recovery
Dimensions shown in inches and (mm).
OUTLINE DIMENSIONS
14-Pin Cerdip (Q) Package
Ceramic Chip Carrier
20-Terminal Leadless
E-20A
REV. B