Search Results

Looking to push the limits of low-noise performance? This application note explores advanced amplifier techniques using Linear Systems’ LSK389 , a monolithic dual N-channel JFET known for its industry-leading noise specs and precision matching. 📄 Dive into design details and circuit techniques that make the LSK389 ideal for audio, instrumentation, and sensor applications: https://www.linearsystems.com/applicationnotes/lsk389-app-note #FETFriday #LSK389 #JFET #LowNoise #AnalogDesign #LinearSystems

At Linear Integrated Systems, we’re passionate about crafting the world’s highest performance discrete semiconductors. Today, we’re excited to spotlight an advanced design that exemplifies the exceptional performance of our JFET products: the All-JFET Differential Amplifier .   ⚙️ The Heart of the Design This amplifier circuit, built entirely around JFETs, demonstrates how carefully selected and matched components can create an ultra-low-noise, highly linear amplification stage. Let’s take a closer look at the core building blocks:   🔹 Differential Input Stage The amplifier begins with a balanced differential pair: Q1A/Q1B (LSK489) : Monolithic dual N-channel JFETs Q2A/Q2B (LSJ689) : Complementary dual P-channel JFETs These matched pairs ensure symmetrical operation, significantly reducing offset voltages and maximizing common-mode noise rejection (CMRR).   🔹 Biasing and Current Mirrors Using precision current sources and mirrors, the amplifier achieves rock-solid biasing. This stability is key to delivering consistent gain, minimal distortion, and a clean audio path across temperature swings.   🔹 Push-Pull Output Stage The output section features pairs of LSK170B and LSJ74A JFETs. These push-pull stages combine to provide: Excellent linearity Low output impedance Ability to drive demanding loads, while maintaining the sonic signature of JFETs   🔹 LED Biasing and Decoupling LEDs are cleverly used to stabilize bias points while keeping the amplifier quiet and responsive. Careful capacitor decoupling throughout the circuit ensures that no unwanted noise seeps into the signal path.   🎧 Why Use an All-JFET Amplifier? ✅ Ultra-Low Noise Our JFETs have some of the lowest noise figures in the industry—ideal for high-end audio, test & measurement, and sensor applications.   ✅ High Linearity JFETs’ square-law characteristics deliver sweet, natural-sounding linearity that’s prized in audiophile-grade equipment.   ✅ Common-Mode Noise Rejection Thanks to the differential topology, this amplifier can reject noise that affects both input lines equally—perfect for instrumentation and precision audio.   ✅ Reliability & Thermal Stability Matched pairs like the LSK489 and LSJ689 maintain consistent performance across temperature variations, ensuring your design stays rock-solid.   🔬 Applications in the Real World From audio preamplifiers  in recording studios to sensor front-ends  in medical equipment and aerospace systems, this all-JFET differential amplifier topology ensures performance that professionals rely on.   This diagram showcases how Linear Integrated Systems’ JFETs—like the LSK489, LSJ689, LSJ74A, and LSK170B—work together to create an amplifier that excels in sonic purity and technical performance.   💡 Ready to Build or Learn More? If you’re designing a precision amplifier or want to see how our JFETs can elevate your next project, get in touch! Visit www.linearsystems.com to stay updated on the latest application notes, product releases, and technical insights.

Creating unique pedal effects doesn’t always require complex circuitry. In fact, many classic sounds are built by simply overdriving a JFET amplifier, tweaking input signals, or using clever circuit designs to shift filter center frequencies. For instance, a single JFET amplifier  can produce a clean, natural-sounding signal— as long as the input voltage remains within the normal operating range  of the amplifier. This depends on the JFET’s gain and the supply voltage you’re using. Once you start pushing the input beyond these typical limits, that’s when the magic of overdrive and harmonic color begins to emerge. Check out the circuit diagram  and simulation data  below to see how this basic building block can become the heart of your next creative pedal design! Figure 1 - A common source amplifier, based on a JFET, is the basis for the design of distortion pedal effect circuit. Figure 2 - The output of the JFET amplifier shows little distortion Figure 3 - Examination of the FFT, one can see that the 2nd and 3rd harmonics are all below 20 dB of the 1st harmonic (300 Hz) In order to introduce some overdrive distortion, the input signal is increased to 3 Volts peak to peak. The resultant output waveform is given below. As can be seen, it is asymmetrically clipped at the top. Figure 4 - Applying a 3 Volt peak-to-peak input signal to the JFET amplifier results in significant distortion. In this case the top of the waveform is clipped.  The Fast Fourier Transform, below, indicates that the harmonics generated at 600 Hz, 900 Hz and 1200 Hz are significant (near 0 dB).  When the distorted and non-distorted waveforms are listened to on Microsoft’s Media Player you can discern the difference. The bass sound has been muted significantly. Figure 5 - Overdriving the JFET amplifier generates 2nd and 3rd harmonics that overpower the 1st harmonic Instead of overdriving the circuit, you can lower the power supply to produce a softer tone. The figure below is the waveform generated (Vout1) when the power supply was lowered to 5 V and the source resistor increased to 1000 Ohm. Figure 6 - A softer tone (Vout1) is produced with a 0.5 Volt peak-to-peak input signal and 5 Volt supply voltage Comparing the FFT of the 5 Volt with the 15 Volt circuit, one sees that the 600 Hz harmonic has been reduced to around -40 dB. When comparing the actual audio of the two circuits, one can hear the difference. The audio of the 5 V circuit is much more subdued than the 15 Volt overdriven circuit.   Figure 7 - Lowering the supply voltage to 5 Volts reduces the level of the 2nd harmonic of the output signal (Vout1) For a more detailed discussion of distortion circuits, see the article by R. G. Keen, A Musical Distortion Primer

At Linear Systems, we're continually inspired by the creative ways engineers use discrete components like JFETs to build elegant analog solutions. This Friday FET Design  features a voltage-integrating light meter  that leverages a Siemens BPX 63 photodiode  for exceptional low-light sensitivity, combined with a clever JFET-based feedback network to control integration timing and minimize distortion. 📐 Circuit Overview This design ensures that only useful light  is used to affect aperture control—excluding noise and ambient artifacts. It also offers fast recovery from light bursts , critical when operating in unpredictable lighting environments such as astrophotography or low-light film capture. ⚙️ Key Features: Photodiode BPX 63 : Delivers 10 nA/lux sensitivity. JFET T1 & T2 : Manage fast recovery and low-noise gate control. High-Gain Amplification : Amplification exceeds 3000 when S1 and S2 open. C1 Capacitor Integration : Produces a linear voltage output  based on incident light. T3 Feedback Switch : Ends exposure when output reaches 1V, improving timing accuracy. +/-3V Supply : Ideal for compact, portable designs. 🧠 How It Works: When the camera shutter is closed, S1 and S2 are closed , shorting the op-amp’s feedback loop through T1, preventing unnecessary charge accumulation. As the shutter opens , S1 and S2 open , and the amplifier gain increases. The integrating capacitor C1  starts charging with the photocurrent. When voltage reaches 1V , T3 (BCW 60)  conducts, signaling the end of exposure by discharging the load path and resetting the system. This buffered design improves upon classic drain-to-gate feedback by taking global feedback from the op-amp’s output (U1A), reducing distortion and enabling operation at higher frequencies. The use of discrete JFETs  in key signal paths ensures minimal noise and excellent control characteristics. 📊 Applications: Light-integrating exposure meters Scientific photometry Low-light measurement instrumentation 🔍 Learn more about high-performance JFETs and analog design at: www.linearsystems.com 💡 Follow us for more design insights every #FETFriday!

In precision analog applications, minimizing distortion while maintaining frequency response is essential when implementing a voltage-controlled resistor (VCR) using an N-Channel JFET. One effective method to achieve this is through buffered global feedback . In this design, the feedback path to the JFET gate is derived from the output of an op-amp (U1A) rather than using a traditional drain-to-gate feedback resistor. The feedback network, composed of R3 and R4, connects the op-amp output directly to the gate, allowing for: Significantly Reduced Signal Distortion:  Buffered feedback isolates the gate drive from the drain voltage, improving linearity across the operating range. Improved High-Frequency Response:  Because the feedback is sourced from the op-amp, R3 and R4 values can be lower, resulting in minimized parasitic capacitance effects and broader bandwidth operation. This architecture removes the need for a direct feedback resistor across the JFET and enables the VCR to perform effectively at higher frequencies compared to conventional approaches. For design engineers focused on optimizing low-noise and high-linearity circuits, this method offers a robust solution using N-Channel JFETs. Reference: EDN - A Guide to Using FETs for Voltage-Controlled Circuits, Part 2 Learn more about Linear Systems' ultra-low-noise, precision JFET solutions at www.linearsystems.com . #LinearSystems #VCRDesign #JFET #LowNoiseDesign #AnalogEngineering #HighFrequencyCircuits #FETDesign

When designing ultra-sensitive analog systems, noise performance isn’t just a feature—it’s a necessity. At Linear Systems, we understand that low-noise discrete components are crucial for high-performance signal chains. This insight drives our LSK389 Series Ultra-Low Noise, Monolithic Dual N-Channel JFET , which has set the standard for engineers worldwide. 100% Noise Tested – The Industry First Linear Systems' LSK389 is now 100% noise tested . This guarantees that 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 . In these scenarios, extremely low-noise signal amplification is crucial. Common 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 these systems, signals travel farther and faster underwater than through air. JFET-based amplifier circuits are essential for capturing and processing these signals cleanly. The LSK389’s ultra-low noise, tight matching, and high input impedance make it a top choice for precision front-end amplifiers 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 over discrete or non-monolithic dual JFETs. 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, which includes: LSK170 – N-channel single version LSJ74 – P-channel equivalent LSK489 – N-channel dual (lower capacitance, slightly higher noise) LSJ689 – P-channel dual version Each component is part of Linear Systems' Improved Standard Products® . They provide lower noise than competitors’ equivalents, making them an ideal choice for engineers focused on performance. Applications Beyond Underwater Systems While the LSK389 excels in underwater acoustic systems, its applications extend into other fields as well. High-End Audio Equipment In high-fidelity audio systems, the clarity of sound is paramount. The LSK389 can significantly improve audio quality by minimizing unwanted noise. Its characteristics ensure that even the faintest sounds are captured with precision. Sensitive Sensor Systems For environmental monitoring, sensors used in industries like meteorology or oceanography require high sensitivity and low noise. The LSK389 ensures that these sensors perform optimally, delivering accurate data without interference from electronic noise. Research and Development In any R&D scenario where analog signal integrity is essential, the LSK389 proves invaluable. Researchers rely on its consistent performance to develop innovative solutions across various technologies. Conclusion Low-noise performance is critical in analog systems, and the LSK389 Series provides unparalleled performance. As it continues to serve multiple industries, the LSK389 remains a cornerstone for those who demand excellence. 📞 For more information, contact us at (510) 490-9160 or sales@linearsystems.com 🌐 Visit: www.linearsystems.com

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 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

Circuit schematic for an Automatic Gain Control (AGC) used in radar self-driving and drone applications, featuring operational amplifiers, diodes, and resistors to regulate signal amplitude. This automatic gain control (AGC) circuit features a non-inverting op-amp with a voltage-controlled resistor — a JFET — that adjusts the amplifier’s gain. The output drives a full-wave rectifier, which feeds an integrator acting as a low-pass filter to minimize ripple and distortion. Using an op-amp diode topology, the circuit produces a full-wave rectified DC signal, controlling the JFET’s drain-to-source resistance. This dynamic resistance adjusts the amplifier’s gain to maintain a consistent 0.2 V peak-to-peak output. Originally designed for radar-based object detection, this AGC approach can be extended to drones, unmanned vehicles, and self-driving cars. 📚 Source: C. Marco, Automatic Gain Control Operates Over Two Decades , Electronics, Aug. 16, 1973; reprinted in Circuits for Electronics Engineers , Electronics, 1977. 🔎 Explore industry-leading JFETs at www.linearsystems.com 💡 Follow us for more #FETFriday insights!

Silicon Valley is synonymous with innovation and technology. At the heart of this region's technological advancement lies the semiconductor industry, a dynamic sector that has fostered the growth of countless companies, products, and technologies. Semiconductors are essential components in modern electronics, powering everything from smartphones to cars, and their significance cannot be overstated. Understanding the Semiconductor Industry The semiconductor industry involves the design, manufacture, and sale of semiconductor devices. These devices are made from materials that have electrical conductivity between that of a conductor and an insulator. Silicon, which gives Silicon Valley its name, is the most widely used semiconductor material. It’s essential in the production of integrated circuits (ICs), which underpin almost every electronic device we use today. Globally, the semiconductor market was valued at approximately $422 billion in 2021, with expectations to surpass $550 billion by 2028. This rapid growth can be attributed to the rise of new technologies, including artificial intelligence (AI), machine learning, the Internet of Things (IoT), and the expanding demand for consumer electronics. As these technologies evolve, the role of semiconductors becomes even more critical. Close-up view of semiconductor chips exemplifying intricate design and technology. The Role of Silicon Valley in the Semiconductor Industry Silicon Valley's influence on the semiconductor industry is substantial. The region is home to many of the world’s leading semiconductor companies and startups that drive innovation. This dynamic ecosystem is nurtured by an abundance of skilled engineers, access to venture capital, and a collaborative spirit among industry players. Many critical advancements in semiconductor technology originated in Silicon Valley. Companies here are constantly pushing the boundaries, developing smaller, faster, and more efficient chips. These advancements are pivotal in meeting the growing demands of the tech landscape. Customer-Driven Innovation The semiconductor industry is heavily customer-driven, with feedback from device manufacturers shaping product development. Companies like Intel and NVIDIA actively collaborate with partners to design semiconductors tailored to specific applications, ensuring components meet the rigorous needs of sectors like automotive, aerospace, and consumer electronics. The rise of electric vehicles (EVs) is a clear example—pushing semiconductor companies to create specialized solutions that manage complex computations, sensors, and connectivity. High angle view of a semiconductor manufacturing plant showcasing a clean and organized workspace. Spotlight on Silicon Valley’s Semiconductor Leaders Top 5 Companies in Silicon Valley: Intel Corporation  – A pioneer in microprocessors and a longtime industry leader. NVIDIA Corporation  – Known for innovations in GPUs, AI, and machine learning technologies. Broadcom Inc.  – Specializes in wired and wireless communication solutions. Qualcomm Inc.  – A leader in mobile communication and 5G technology. Advanced Micro Devices (AMD)  – A major player in microprocessors and GPUs. These companies have helped position Silicon Valley as a global semiconductor powerhouse. Where Linear Systems Fits In Among Silicon Valley’s network of innovators, Linear Integrated Systems, Inc.  stands out for its focus on precision small-signal discrete semiconductors . Founded in 1987 in Fremont, California, Linear Systems designs and manufactures ultra-low-noise JFETs, DMOS switches, and other critical components used in highly demanding applications—ranging from underwater acoustics  and defense systems  to professional audio equipment and medical instrumentation . Linear Systems is unique in that it combines classic Silicon Valley craftsmanship with modern demands for performance and reliability. Its parts, such as the LSK389 Ultra-Low-Noise Dual JFET  and LSK170 Single JFET , are key to advancing technologies in sectors that demand the highest levels of precision. By maintaining control over its design and manufacturing processes, Linear Systems provides unmatched quality and is a trusted partner for companies that require ultra-low-noise solutions and rigorous component performance. Eye-level view of a semiconductor research laboratory focusing on technological advancement and innovation. Emerging Trends in the Semiconductor Industry As technology evolves, so too does the semiconductor industry. Key trends include: Artificial Intelligence and Machine Learning: Specialized AI chips are driving a new era of data processing efficiency. IoT Integration: The demand for reliable, low-power semiconductors continues to surge with IoT growth. Supply Chain Resilience: Companies are rethinking production strategies to localize manufacturing and mitigate risks. Sustainability Initiatives: Focus on reducing environmental impact and increasing energy efficiency in chip production. Advanced Packaging Technologies: Innovations like 3D stacking and system-on-chip (SoC) designs are improving performance and miniaturization. Future Outlook for Silicon Valley's Semiconductor Sector The semiconductor industry's future in Silicon Valley is incredibly bright. Ongoing advancements in AI, autonomous systems, renewable energy, and connected devices will continue driving demand for cutting-edge semiconductor technologies. Companies like Linear Systems, Intel, NVIDIA, and others will play a crucial role—not just in providing components, but in leading the next wave of innovation  across industries worldwide. Collaboration with universities, research institutions, and customer-driven development will remain essential. Those companies that adapt to rapid technological shifts and prioritize R&D will continue to thrive. In conclusion, Silicon Valley remains at the forefront of semiconductor innovation, with companies like Linear Systems  embodying the region’s spirit of precision, innovation, and leadership . As the world becomes more connected and technology-dependent, Silicon Valley’s influence on the semiconductor industry—and by extension, on the future of technology itself—will only grow stronger. For more information about precision discrete semiconductors and how they enable cutting-edge applications, 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 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 .