a FEATURES 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 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
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) process. 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 temperature range. 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.
Precision, Low Cost Dual BiFET Op Amp AD642 PIN CONFIGURATION
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 hermeticallysealed, TO-99 metal can or available in chip form. PRODUCT HIGHLIGHTS
1. The AD642 has tight matching specifications to ensure high performance, eliminating the need to match 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 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), 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.
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