The LSK489 is a monolithic dual ultra-low-noise junction field effect transistor (JFET) optimized for use in high-end sensor front-end amplification designs. Linear Systems introduced the component originally in 2013 and it was quickly embraced by leading audio designs and the builder community, being named one of the most important electronics industry innovations for the year. The re-released part is now available in two Idss grades, enabling engineers to more closely match the part's performance to their circuit designs. The part is available in TO-71, SOIC-A, SOT-23 and DFN packages, as well as bare die.
"The LSK489 is one of the world's premier junction field-effect transistors, but designers needed more precise performance grading to match the part's capabilities with their design requirements," says Linear Systems President Tim McCune. "Supported by a detailed datasheet and a multi-design application note, this component is the best option available for a wide range of products."
The component's benefits include a common mode rejection ratio over 100dB; tight differential voltage match versus current; improved op amp speed settling time accuracy; minimum input error trimming error voltage; and lower intermodulation distortion due to low input capacitance. A detailed Datasheet and Application Note written by Bob Cordell, as well as the original audio design note for an headphone amplifier written by Dimitri Danyuk are all available.
Tim McCune adds that the part achieves very low noise with respect to its transconductance, which is attributed to Linear Systems' ability to eliminate almost all of the generation-recombination noise usually present in JFETs. "The advances we've made in JFET wafer fabrication have enabled us to squeeze even more noise out of this part while retaining the classic performance of our monolithic dual JFET line," he says. "The matching, common-mode rejection ratio and other key performance parameters are as impressive as the ultra-low noise this part has."
With a unique combination of low noise and low input capacitance, the LSK489 enables highly capable front-end amplification for high-end applications, such as the Rubin Observatory. The part was selected by designers of the Rubin Observatory/Large-Scale Synoptic Telescope astronomical observatory, currently under construction in Chile, for its superior overall performance and high reliability. The images recorded by the observatory's 3.2-gigapixel CCD imaging camera, the largest digital camera ever constructed, flow through 2,000 LSK489s comprising the project's initial amplification circuit.
Linear Systems specializes in the development and manufacture of precision, ultra-low-noise small-signal discrete components. Its parts, such as the LSK389 and LSK489, are used in highly demanding sensor systems ranging from ribbon microphones to piezoelectric devices to sonobuoys. This announcement comes short after Linear Systems also re-release the low-noise, low-cost LS844 series dual JFET, an evolution of a classic dual JFET developed and introduced by Linear Systems over 20 years ago. These parts also provide the front-end amplification for high-end test and measurement, medical and audio equipment.
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