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LSK389 Press Release

Mar 17, 2023

Ultra-Low Noise, Monolithic Dual, N-Channel JFET

Industry’s First 100% Noise Tested, Ultra-Low Noise, Monolithic Dual, N-Channel JFET

FREMONT, CA - 01/21/2020 - Linear Systems announces the re-release of their most popular part, the LSK389 Series, Ultra-Low Noise, Monolithic Dual, N-Channel JFET, now 100% tested to meet or exceed noise specifications.

The LSK389 is the lowest noise Junction Field Effect Transistor (JFET) in its class and has been used in ultra-high-end applications for over a decade. The LSK389 enables developers to create the lowest noise signal chains possible for sensors, professional audio equipment and other applications.

Linear Systems is releasing the LSK389 after creating the capability for individual screening of small-signal discrete components to levels below a billionth of a volt (nV/√Hz) of noise in quantities up to tens of thousands of parts. This testing capability – the only one in existence worldwide – ensures all LSK389s leaving the factory produce no burst (RTN or popcorn) noise and meet or exceed 1/f and broadband noise specifications. 

The LSK389, Ultra-Low Noise, Monolithic Dual, N-Channel JFET provides designers with a better-performing solution for obtaining tighter IDSS matching and better thermal tracking than using individual JFETs or non-monolithic dual JFETs. The part is an ideal combination of high transconductance, ultra-low noise and relatively low input capacitance.

The LSK389 is the lead part of Linear Systems’ family of low-noise JFETs. The LSK170 is the N-channel single version of the LSK389, and the LSJ74 is the P-channel counterpart to the LSK170. The N-channel dual LSK489 has slightly higher noise but lower input capacitance than the LSK389, and the LSJ689 is its P-channel dual counterpart.  In addition to the LSK-series, all Linear Systems’ JFET standard products have substantially lower noise than those made by other manufacturers and are marketed under the Improved Standard Products ® trademark.

“The LSK389 is the key to building the world’s lowest-noise signal chains for many applications,” Linear Systems President Tim McCune said.  “Creating our new testing capability enables us to guarantee each part we ship meets our ultra-low noise spec, and that no manufacturer will ever have to scrap a circuit board because these parts didn’t work correctly.”

Linear Systems is a full-service, privately-held, 32-year-old designer and manufacturer of small-signal discrete semiconductors. The Fremont, CA-based company was founded by John H. Hall, co-founder of Intersil and founder of Micro Power Systems.

Linear Systems specializes in the development and manufacture of precision, ultra-low noise small-signal discrete components. Its parts are used in highly demanding sensor systems ranging from the Large-Scale Synoptic Telescope to piezoelectric devices to sonobuoys. These parts also provide the front-end amplification for high-end test and measurement, medical and audio equipment.

In addition to providing parts and technical support for new designs, Linear Systems supplies pin-for-pin replacements for more than 2,000 discrete devices currently offered or discontinued by National Semiconductor, Siliconix-Vishay, Intersil, Motorola, Fairchild and Toshiba.

Contact the factory for lower noise and other specification selections.

Summary of Features:

  • Ultra-Low Noise: en = 1.3nV/√Hz (typ), f = 1.0kHz and NBW = 1.0Hz

  • Four grades of IDSS: 2.6-6.5mA, 6.0-12.0mA, 10.0-20.0mA and 17-30mA, with an IDSS match of 10 percent

  • Tight Matching: IVGS1-2I = 15mV max

  • High Breakdown Voltage: BVGSS = 40V max

  • High Gain: Gfs = 20mS (typ)

  • Relatively Low Capacitance: 25pF (typ)

  • Available in surface mount SOIC 8L and thru-hole TO-71 6L packages.


  • Improved Signal Chain Noise Performance

  • Better Matching and Thermal Tracking Due To Unique Monolithic Interleaved Dual Design Construction

  • Better Performance for Battery Operated Applications by Providing a Wide Output Swing


  • Ultra-sensitive sensor applications

  • Audio Amplifiers and Preamps

  • Discrete Low-Noise Operational Amplifiers

  • Battery-Operated Audio Preamps

  • Audio Mixer Consoles

  • Sonic Imaging

  • Instrumentation Amplifiers

  • Microphones

  • Sonobuoys

  • Hydrophones

  • Chemical and Radiation Detectors

Price: 1,000+ pieces of the LSK389A SOIC 8L package is $4.67 (USD) each.  1,000+ pieces of the LSK389A TO-71 6L package is $6.70 (USD) each.  Prices vary based on grade (A, B, C and D) and quantity. Availability: Production quantities available now.Delivery: Factory stock to 8 weeks. For More Information: Call Linear Systems toll free phone number: (800) 359-4023, regular business line: (510) 490-9160 or fax: (510) 353-0261.Email: Website:  

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