Matched Offset Voltage
Matched Offset Voltage Over Temperature
Matched Bias Current
Crosstalk: –124 dB @ 1 kHz
Low Bias Current: 35 pA max Warmed Up
Low Offset Voltage: 500 V max
Low Input Voltage Noise: 2 V p-p
High Open Loop Gain
Low Quiescent Current: 2.8 mA max
Low Total Harmonic Distortion
Standard Dual Amplifier Pin Out
Available in Hermetic Metal Can Package and Chip Form
MIL-STD-883B Processing Available
Single Version Available: AD542
Precision, Low Cost
Dual BiFET Op Amp
The AD642 is a pair of matched high speed monolithic BiFET
operational amplifier fabricated with the most advanced bipolar,
JFET and laser trimming technologies. The AD642 offers
matched bias currents that are significantly lower than currently
available monolithic dual FET input operational amplifiers:
35 pA max matched to 25 pA for the AD642K and L; 75 pA
max, matched to 35 pA for the AD642J and S. In addition, the
offset voltage is laser trimmed to less than 0.5 mV and matched
to 0.25 mV for the AD642L, 1.0 mV and matched to 0.5 mV for
the AD642K, utilizing Analog’s laser-wafer trimming (LWT)
The tight matching and temperature tracking between the
operational amplifiers is achieved by ion-implanted JFETs and
laser-wafer trimming. Ion-implantation permits the fabrication of
precision, matched JFETs on a monolithic bipolar chip. The
optimizes the process to product matched bias currents which
have lower initial bias currents than other popular BiFET op
amps. Laser-wafer trimming each amplifier’s input offset voltage
assures tight initial match and combined with superior IC
processing guarantees offset voltage tracking over the tempera-
The AD642 is recommended for applications in which excellent
ac and dc performance is required. The matched amplifiers
provide a low-cost solution for true instrumentation amplifiers,
log ratio amplifiers, and output amplifiers for four quadrant
multiplying D/A converters such as the AD7541.
The AD642 is available in four versions: the ‘‘J’’, ‘‘K’’ and ‘‘L,’’
all specified over the 0°C to +70°C temperature range and one
version, ‘‘S,’’ over the –55°C to +125°C extended operating
temperature range. All devices are packaged in the hermetically-
sealed, TO-99 metal can or available in chip form.
1. The AD642 has tight matching specifications to ensure high
performance, eliminating the need to match individual
2. Analog Devices, unlike some manufacturers, specifies each
device for the maximum bias current at either input in the
warmed-up condition, thus assuring the user that the AD642
will meet its published specifications in actual use.
3. Laser-wafer-trimming reduces offset voltage to as low as
0.5 mV max and matched side to side to 0.25 mV
(AD642L), thus eliminating the need for external nulling.
4. Low voltage noise (2 µV, p-p), and high open loop gain
enhance the AD642’s performance as a precision op amp.
5. The standard dual amplifier pin out allows the AD642 to
replace lower performance duals without redesign.
6. The AD642 is available in chip form.
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
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