Dual High Speed,
Implanted BiFET Op Amp
Matched Offset Voltage
Matched Offset Voltage Over Temperature
Matched Bias Currents
Crosstalk –124 dB at 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 Slew Rate: 13 V/s
Low Quiescent Current: 4.5 mA max
Fast Settling to ؎0.01%: 3 s
Low Total Harmonic Distortion: 0.0015% at 1 kHz
Standard Dual Amplifier Pinout
Available in Hermetic Metal Can Package
and Chip Form
MIL-STD-883B Processing Available
Single Version Available: AD544
AMPLIFIER NO. 1
AMPLIFIER NO. 2
PIN 4 CONNECTED TO CASE
The AD644 is a pair of matched high speed monolithic FET in-
put operational amplifiers fabricated with the most advanced bi-
polar, JFET and laser-trimming technologies. The AD644 offers
matched bias currents that are significantly lower than currently
available monolithic dual BiFET operational amplifiers: 35 pA
max, matched to 25 pA for the AD644K and L, 75 pA max
matched to 35 pA for the AD644J and S. In addition, the offset
voltage is laser trimmed to less than 0.5 mV, and matched to
0.25 mV for the AD644L, 1.0 mV and matched to 0.5 mV for
the AD644K, utilizing Analog Devices’ laser-wafer trimming
The tight matching and temperature tracking between the op-
erational 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. This
process optimizes the ability to produce matched amplifiers
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 superior IC processing
guarantees offset voltage tracking over the temperature range.
The AD644 is recommended for applications in which both
excellent ac and dc performance is required. The matched am-
plifiers provide a low cost solution to true wideband instrumen-
tation amplifiers, low dc drift active filters and output amplifiers
for four quadrant multiplying D/A converters such as the
AD7541, 12-bit CMOS DAC.
The AD644 is available in four versions: the “J”, “K” and “L”
are specified over the 0°C to +70°C temperature range and the
“S” over the –55°C to +125°C operating temperature range.
All devices are packaged in the hermetically sealed, TO-99
metal can or available in chip form.
1. The AD644 has tight side to side matching specifications to
ensure high performance without matching individual devices.
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 AD644
will meet its published specifications in actual use.
3. Laser-wafer-trimming reduces offset voltage to as low as
0.5 mV max matched side to side to 0.25 mV (AD644L),
thus eliminating the need for external nulling.
4. Improved bipolar and JFET processing on the AD644 result
in the lowest matched bias current available in a high speed
monolithic FET op amp.
5. Low voltage noise (2 µV p-p) and high open loop gain
enhance the AD644’s performance as a precision op amp.
6. The high slew rate (13.0 V/µs) and fast settling time to
0.01% (3.0 µs) make the AD644 ideal for D/A, A/D, sample-
hold circuits and dual high speed integrators.
7. Low harmonic distortion (0.0015%) and low crosstalk
(–124 dB) make the AD644 an ideal choice for stereo audio
8. The standard dual amplifier pin out allows the AD644 to
replace lower performance duals without redesign.
9. The AD644 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.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.