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When it comes to designing ultra-sensitive analog systems, noise performance isn’t a feature—it’s a necessity. At Linear Systems, we understand the critical role that low-noise discrete components play in high-performance signal chains. That’s why our LSK389 Series Ultra-Low Noise, Monolithic Dual N-Channel JFET  continues to set the standard for analog engineers across the globe. 100% Noise Tested – The Industry First Originally re-released in 2020, the LSK389 is now 100% noise tested  to guarantee it meets or exceeds both 1/f and broadband noise specifications. Using the world’s only large-scale sub-nanovolt testing capability, Linear Systems screens each unit to ensure: No burst noise (RTN or popcorn) Ultra-low noise performance down to 1.3nV/√Hz (typ) Whether you're building high-end audio equipment, ultra-sensitive sensors, or low-noise op amps, you can rely on consistent, production-grade noise performance. Trusted in Underwater Acoustic Systems The LSK389  and its single-device counterpart, the LSK170 , are widely used in underwater acoustic applications  where extremely low-noise signal amplification is essential. These applications include: Sonobuoys  used in anti-submarine warfare (ASW) Towed array sonar systems  for naval surveillance Hydrophones  for marine research and underwater audio detection Underwater modems and transducers  for acoustic communication and navigation Passive and active sonar systems  used in defense and industrial marine applications In all of these systems, signals travel farther and faster underwater than through air, and JFET-based amplifier circuits are required to cleanly capture and process those signals. The LSK389’s ultra-low noise, tight matching, and high input impedance make it a top choice for these precision front-end amplifiers  that are vital to sonar and underwater communications equipment. Why the LSK389? The LSK389 isn’t just another low-noise JFET. Its monolithic interleaved dual construction  provides superior IDSS matching, better thermal tracking, and performance advantages that discrete or non-monolithic dual JFETs can’t match. Key Features: Four IDSS grading options for design flexibility Tight matching: IVGS1-2 ≤ 15mV max High gain: Gfs = 20mS (typ) Low capacitance: 25pF (typ) Available in SOIC-8 and TO-71 packages Part of a Complete Low-Noise JFET Family The LSK389 is the cornerstone of our low-noise JFET lineup: LSK170  – N-channel single version LSJ74  – P-channel equivalent LSK489  – N-channel dual (lower capacitance, slightly higher noise) LSJ689  – P-channel dual version Each is part of Linear Systems' Improved Standard Products® , offering lower noise than competitors' equivalents. 📞 For more information, contact us at (510) 490-9160  or sales@linearsystems.com 🌐 Visit: www.linearsystems.com

🔬 Exploring the Reversed Sziklai Pair  🔍 Check out this clever hybrid design that flips the script on traditional amplifier topology!   📌 What makes it interesting? – Bipolar input = lower input impedance– Wide input range: 0.1mV to 12mV– Frequency response: 100Hz – 620kHz– Voltage gain ≈ 100 | Current gain ≈ 1.5– Distortion as low as 0.89%   This design demonstrates how blending technologies can lead to simple yet effective results in audio and signal processing. A great example of innovation through circuit simplicity.   📄 Source: https://iopscience.iop.org/article/10.1088/1757-899X/225/1/012152/pdf   Explore industry-leading JFETs at: www.linearsystems.com 💡 Follow us for more #FETFriday insights! #AnalogDesign #JFET #BipolarTransistors #AudioEngineering #CircuitDesign #ElectronicsInnovation

Linear Integrated Systems headphone amplifier evaluation board is a complete, low-power stereo audio amplifier for high-fidelity line-level output and headphone applications. It consists of Linear Integrated Systems JFETs along with a number of other parts mounted on a circuit board. Linear Integrated Systems headphone amplifier evaluation board includes the following features: Stereo, single ended input and single ended output 400 mW output power into 100Ω Wide frequency response (10Hz?200kHz; ?1dB) Voltage gain 5 (14dB) Low distortion (THD+N is less than 1% at 10Hz?20kHz at 5Vrms into 100Ω and less than 0.1% from 10 Hz to 20 kHz at 1Vrms into 100Ω load) Short circuit protection Pop reduction (slow start) circuit Defeatable cross feed circuit Volume control Overvoltage and reverse polarity power protection Audio input and output connections: left and right RCA phono jack inputs, ¼” stereo phone jack output External 9V–16V supply input External power supply connector: power jack, inside diameter 2.1mm, outside diameter 5.5mm

Linear Systems has introduced the LSK489, a monolithic dual N-Channel JFET engineered to deliver exceptional performance in both audio and instrumentation applications. This component stands out due to its ultra-low noise characteristics, with a typical noise density of 1.8 nV/√Hz at 1 kHz, ensuring minimal signal interference in sensitive analog circuits. A notable feature of the LSK489 is its remarkably low input capacitance of 4 pF, significantly lower than comparable JFETs, which often exhibit capacitances around 25 pF. This reduced capacitance minimizes intermodulation distortion and allows for simpler circuit designs without the need for complex cascode configurations that can introduce additional noise. The device's design includes interleaved JFETs on the same silicon die, providing excellent matching and thermal tracking between the two channels. This construction ensures consistent performance across varying temperatures and operating conditions, making it ideal for precision applications. The LSK489 is available in multiple package options to accommodate diverse design requirements: TO-71 6L : A through-hole metal can package offering robust performance. SOIC 8L : A surface-mount option facilitating compact designs. SOT-23 6L : A smaller surface-mount package suitable for space-constrained applications. All versions are RoHS-compliant, aligning with environmental and safety standards. In terms of electrical characteristics, the LSK489 offers a gate-to-source cutoff voltage ranging from -1.5 V to -3.5 V and a drain-to-source saturation current (IDSS) between 2.5 mA and 15 mA, depending on the grade. These specifications provide designers with flexibility in biasing and application suitability. The LSK489 is particularly well-suited for applications requiring high input impedance and low noise, such as: Microphone Preamplifiers : Enhancing audio signal fidelity. Phono Preamplifiers : Improving the quality of vinyl record playback. Instrumentation Amplifiers : Ensuring precise measurements in scientific equipment. Acoustic Sensors : Capturing accurate sound measurements in various environments.

Linear Systems, a world-class producer of ultra-low-noise JFETs and other small-signal discrete semiconductors, announces the large-scale availability of five of its top-performing components. These components, ranging from low-noise monolithic dual JFETs to small-signal MOSFETs, are available in wafer form in quantities ranging from one million to ten million for immediate packaging and shipment. All parts meet Linear Systems' industry-leading datasheet specifications and are available for fast delivery due to substantial buffer stock of wafers. Parts available for shipment include : 1.  LS844 Monolithic Dual Small-Signal JFET:   One million dice in wafer form in stock. This low-noise front-end amplifier features high Common Mode Rejection Ratio and excellent matching over a wide range of temperatures. [Download Data Sheet] 2. 3N163 Small-Signal MOSFET : Three million dice in wafer form in stock. Ideal for sensor applications such as gas detection and piezo devices, with half the noise of competitors' parts. [Download Data Sheet] 3. LS320 BiFET Amplifier:    1.3 million dice in wafer form in stock. A high-input impedance, single monolithic amplifier, designed as a direct replacement for Amperex equivalent parts. Perfect for high impedance sense amplifier applications. [Download Data Sheet] 4. 2N/PN/SST4391 N-Channel JFET Series:    2.5 million dice in wafer form in stock. This single, low-noise N-channel JFET switch is ideal for low-noise, high-gain, low-resistance switching and amplifier applications. [Download Data Sheet] 5. 2N/PN/SST4117A N-Channel JFET Series:   14.3 million dice in wafer form in stock. This single, low-capacitance, ultra-high-input-impedance N-channel JFET amplifier is a direct replacement for Fairchild, NXP, and Siliconix-Vishay parts. [Download Data Sheet] These parts are also available in bare die and sorted wafer form. In addition to these million-plus parts inventories, Linear Systems keeps substantial quantities of all its parts on hand, including the industry-leading LSK389 monolithic dual N-channel ultra-low-noise JFET. About Linear Systems Founded in 1987, Linear Systems is a Silicon Valley-based designer, manufacturer, and seller of precision, high-performance, small-signal discrete semiconductors. Linear Systems produces ultra-low-noise monolithic dual and single JFETs, bipolar transistors, high-speed DMOS switches, small-signal MOSFETs, ultra-low-leakage diodes, and BiFET amplifiers. These parts are designed into world-class products in fields such as Test & Measurement, Audio, Scientific Optical, Military Sensor, Hydrophone/Sonobuoys, Industrial Controls, and Hybrids. For more information, visit www.linearsystems.com .

When John Kurlander sought to capture the vast array of sound for the  Lord of the Rings  movies, he turned to Wes Dooley and his ribbon microphones. And for years, when Wes needed ultra-low-noise semiconductors to build and amplify those microphones, he turned to Linear Systems, Inc. “Linear Systems has kept that tradition going of making parts that are competitive with the [discontinued Toshiba] SK170s and 389s,” Dooley said in a recent interview. “And that gives us the ability to make compact, high-performance audio products.” “We make the quietest ribbon mic in the world, the A440, and the higher SPL A840. Both of them use the [Linear Systems] LSK389, for the output drivers and their current supply,” Dooley said. Dooley's company, Audio Engineering Associates (AEA), also uses the LSK389 in front ends of its RPQ and RPQ 500 preamplifiers, which were designed for use with ribbon microphones. AEA's microphone business started with ribbon mics for classical music used as movie scores. “John Kurlander did all three Lord of the Rings using AEA mics on strings left and right almost as strong in the mix as the main orchestra mics,” Dooley said. “When you work with such people, one really learns to be of service.” AEA's customer list reads like a Who's Who of Grammy and Academy Award-winning recording engineers and artists. Among the many examples, sound engineer Michael Bishop, winner of eight Grammy awards, extensively uses AEA's A840 microphones and AEA preamps for his recordings. Shawn Murphy, who's worked on over 330 films and won an Academy award for Jurassic Park, also relies on AEA's preamps and microphones. One of the best parts of AEA's website is the  long list of reviews and mentions by users . Dooley, a lifelong ribbon microphone enthusiast and developer, got into the business by repairing ribbon mics built by RCA during the golden age of radio. “We started servicing mics in '76 when RCA shut down making them,” he said. “Many of our favorite RCA designs were from the mid '30s, when a designer's foremost tool was listening to live music. Critical listening was the gold standard as acoustical measurements were cumbersome.” “We've adopted that approach, which is: musicality trumps metrics. The mic has to sound good to people in the music business,” Dooley said. “If it doesn't sound good, measurements don't matter. Once you have a mic that sounds good to people who have experienced ears, then measurements are very important, as they are the key to consistent production.” “So we first strive to make sure it sounds musical, and then we measure what it does,” Dooley said. “Because, as one of my mentors, Richard Heyser, said, if it measures well but doesn't sound right, then you're measuring the wrong things. Often you find you don't know what the right thing to measure is. Over time you discover what those metrics might be. Ultimately, it's a matter of how it sounds. Since we come from an acoustic music tradition, it's pretty simple: you put the mic in front of live music, and compare that live sound with the reproduction, to see how close it is.” Dooley told the story of working with legendary bluegrass fiddle player/violinist Richard Greene. Greene, along with his wife, a violinist with the LA Chamber Orchestra, recorded samples using over 20 microphones. “The next day, when they had 'fresh ears,' they listened to all the recordings and said the one made using our ribbon microphones was the best,” Dooley said. “And that's what we try for, for the musicians to experience that this is the closest they've ever heard to an actual performance.” Asked to comment for this article, Greene had high praise for Dooley and his microphones. “Silky, smooth, best violin sound I ever heard, Wes is amazing and his tech support and other free maintenance are over the top,” Greene wrote. “I will never have any use for any other mic on my violin. I have the AEA 440.” Dooley said this close interaction with artists drives how he builds microphones and preamps. “The whole thing,” he said, “is to build tools they need. That is the key to survival for a small business doing high-performance products.” The LSK389 “is a very good part for manufacturing,” Dooley said. AEA uses the “C” grade of the LSK389. “We started with the 'A' [grade], but then we realized it didn't make any difference for what we were doing,” he said. The LSK389 is graded by IDSS ; all three grades have the same ultra-low-noise characteristics. The Linear Systems LSK389 part used by AEA is an ultra-low-noise junction field effect transistor. Linear System Founder and CEO John H. Hall began working on a JFET similar to Toshiba's 2SK389 about the time that the Japanese company began to discontinue the device 10 years ago. “Toshiba kept its production process for the 389 secret, so we had to figure out on our own how to build something to the same specification, which was extremely difficult,” Hall said. Expertise brought to Linear Systems is based on processes and products Hall developed since 1962 at Amelco, Union Carbide, Intersil, and Micro Power Systems. Hall, a protégé of Silicon Valley legend Dr. Jean Hoerni, was the director of IC Development at Union Carbide, co-founder and vice president of R&D at Intersil, and founder/president of Micro Power Systems. Much of Linear Systems' current development work focuses on lower-noise JFETs. The production techniques Hall conceived to squeeze the last bit of noise out of the 389 led to development of another part, the LSK489. The LSK489 has less transconductance than the 389, and though this increases noise slightly, it makes the part easier to design into new circuits. “While the 389 is the perfect part for some users, such as Wes Dooley, who need the lowest noise levels in existence, we found that the high gate-to-drain capacitance of the 389 caused problems for some of our other customers,” Hall said. “Building a high transconductance part, such as the 389, formed part of the basis for providing ultra-low-noise levels, but the high input capacitance causes intermodulation distortion in some higher-frequency applications,” Hall said. “Since we had created some advanced processing techniques to make the 389, we decided to go back and look at creating a part with lower capacitance using the same processes.” Though Dooley's ribbon microphone and other devices take advantage of the 389's low noise level, other developers could tolerate a slightly higher noise level in a part that has much lower input capacitance due to a lower transconductance, Hall said. The lower capacitance and other features make the LSK489 a lower-noise, functional replacement for Linear Systems' LS840-series of JFETs, as well as the Siliconix U401-403 series. Dooley's precision ribbon microphones are perfect applications of the LSK389, Hall said. “Both ribbon microphones and JFETs are very difficult to design and build, but there's really no other way to achieve the level of performance needed than to do the work this way.” The circuit design work using the LSK389s was done for AEA by Fred Forssell of  http://www.forsselltech.com . For more on Dooley's microphones, go to:  http://www.ribbonmics.com Data sheets for the LSK389 and LSK489, the application notes for the LSK489, and a good paper on general JFET theory and use can be downloaded at:  http://www.linearsystems.com .