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Towed Array Designers — This JFET Was Built for You


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When you’re trying to detect tiny signals at the bottom of the ocean, the front end of your signal chain can make or break the entire system.


Towed arrays, hull-mounted sonars, and underwater acoustic modems all share one unforgiving requirement: you don’t get a second chance at the data. Once noise, drift, or mismatch pollutes a hydrophone’s output, there’s no DSP magic that can fully restore what’s been lost.


That’s why so many designers working with hydrophones and piezoelectric transducers are turning to the LSK389, a monolithic dual N-channel JFET engineered specifically for ultra-low-noise, high-integrity signal capture.


Why the Front-End JFET Matters So Much Underwater


Hydrophones and underwater acoustic sensors often deal with:


  • Extremely low signal levels from distant or low-amplitude sources

  • Long cable runs in noisy, harsh EMI environments

  • Wide temperature swings, especially in deep or varying thermocline conditions

  • High source impedance, which magnifies the impact of input noise and leakage


In these systems, the very first active device — typically a JFET or JFET-input stage — sets the noise floor and stability for everything downstream.


A poorly matched or noisy device at the front end can lead to:


  • Elevated system noise floor

  • Channel-to-channel mismatch across arrays

  • DC offset drift that complicates calibration and beamforming

  • Reduced detection range and degraded SNR


This is exactly the class of problem the LSK389 is designed to solve.


The LSK389: Built for Hydrophones & Acoustic Arrays


The LSK389 is a monolithic dual JFET that delivers:


  • Ultra-low thermal noise: Ideal for very low-level signals at the hydrophone output, helping extend detection range and preserve fine detail.

  • Exceptional VGS tracking: Because both JFETs are on the same die, they track closely over temperature and time. This is especially important in differential and balanced front ends common in towed array systems.

  • Lower offset for cleaner, more stable baselines: Reduced offset makes it easier to calibrate and maintain stable references over long deployments, cutting down on re-trims and compensation complexity.

  • High input impedance for piezoelectric sensors: The LSK389’s very high input impedance allows your hydrophones and transducers to operate as intended, with minimal loading and minimal loss of low-frequency information.


Put simply: the LSK389 is designed to capture more of the ocean — and less of your own system noise.


Ideal Applications in Underwater Acoustics

The LSK389 is a strong fit anywhere low noise, high stability, and tight matching are required, especially in:


  • Towed array hydrophone preamplifiersUse the LSK389 as the input device in differential or charge amplifier topologies to maximize SNR and maintain consistent performance across many channels.

  • Sonar front endsFrom passive listening systems to active sonar receive paths, the LSK389 helps ensure that reflections and echoes aren’t masked by front-end noise.

  • Underwater acoustic modemsModems operating in noisy or bandwidth-constrained environments benefit from clean, low-noise analog front ends that preserve constellation integrity and reduce bit error rates.

  • Transducer conditioning modulesJFET-based front ends with the LSK389 can be used in compact, sealed modules right at the sensor to minimize cable-induced noise.


Design Considerations: Getting the Best from the LSK389


While every design is different, here are a few general tips when using the LSK389 in hydrophone and acoustic applications:


  • Leverage the monolithic dualUse both JFETs in matched configurations (differential pairs, cascoded stages, or balanced inputs) to take full advantage of tight V<sub>GS</sub> tracking.

  • Pay attention to layout and shieldingEven with a low-noise device, poor PCB layout or ground strategy can ruin performance. Keep sensitive nodes short, use solid ground planes, and route noisy digital lines away from the front end.

  • Optimize biasing for your noise and bandwidth targetsBias current affects noise performance. Dial in your operating point for the best trade-off between noise, linearity, and power consumption.

  • Control temperature where possibleWhile the LSK389 is designed for stability, any analog front end benefits from good thermal management, especially in high-density array electronics.


Try the LSK389 in Your Next Towed Array or Hydrophone Design


If you’re designing:


  • Towed arrays

  • Hull-mounted sonar systems

  • Distributed hydrophone networks

  • Underwater acoustic modems or transducer modules


…the LSK389 is an excellent candidate for your front-end JFET.

We’re currently making the LSK389 available to evaluate at no cost, so you can see its performance in your own hydrophone or acoustic array design.


📩 Request samples here and our team will follow up with you to get the right configuration into your lab.

 
 
 

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