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In an era dominated by FETs and IC-level integration, it’s easy to forget just how powerful a well-designed bipolar transistor can be. Yet for the analog engineer chasing ultra-low drift, tight matching, and reliable gain stability, bipolar junction transistors (BJTs) remain indispensable. Linear Systems carries forward the legacy of precision bipolar technology with a complete line of monolithic matched dual and single transistors  designed for low noise, high stability, and long-term reliability in demanding analog applications. Why Bipolar Transistors Still Matter Bipolar transistors offer high transconductance, low offset voltage, and predictable linearity —attributes that make them ideal for precision amplifiers, log converters, and differential front ends. While FETs dominate in high-impedance designs, BJTs remain the preferred choice when low noise at higher currents, tight matching, or excellent gain tracking  over temperature are essential. Linear Systems’ monolithic dual transistors combine those advantages with the consistency of devices fabricated on a single die. The Linear Systems Bipolar Lineup Each device family is built on a foundation of precision matching, temperature stability, and proven analog performance. Series Type Configuration Highlights / Applications IT120 / IT124 Series NPN Monolithic Dual Ultra-low drift, ideal for differential input stages LS310 Series NPN Monolithic Dual Tight beta matching for instrumentation and audio circuits LS318 NPN Monolithic Dual Log conformance for log and transimpedance amplifiers LS301 Series NPN Monolithic Dual High-voltage, super-beta design for precision high-voltage amplifiers LS3250 / LS3250S NPN Dual / Single High-speed switching with excellent gain stability LS3550 Series PNP Dual / Single Complementary to LS3250 series for push-pull amplifier design LS350 / IT130 Series PNP Monolithic Dual Tight matching and tracking for low-offset differential stages LS358 PNP Monolithic Dual Log-conformance PNP pair for current-mode and logarithmic circuits Each part is manufactured on Linear Systems’ precision analog processes to ensure gain, offset, and temperature characteristics remain tightly controlled —a vital advantage for applications where unmatched discretes simply can’t deliver. Monolithic Matching for Real-World Precision Unlike discrete matched pairs mounted side-by-side, Linear Systems’ monolithic dual transistors share the same silicon substrate , ensuring both devices track identically over time and temperature. This results in: Exceptional V_BE and beta matching  across the operating range Reduced thermal drift  and offset voltage Improved common-mode rejection  in differential circuits Long-term stability  ideal for metrology, medical, and instrumentation applications Whether you’re designing a precision current mirror, amplifier front end, or logarithmic converter, these transistors ensure your design behaves predictably across environmental extremes. Applications and Design Examples Linear Systems’ bipolar transistors appear anywhere analog accuracy matters: Instrumentation Amplifiers  – Tight beta matching minimizes offset and drift. Audio Circuits  – Complementary NPN/PNP pairs deliver low distortion and consistent tone. Logarithmic and Transimpedance Amplifiers  – LS318 and LS358 provide superior log conformity. High-Speed Switching  – LS3250S single devices handle rapid switching with excellent gain linearity. Precision Current Mirrors  – Matched pairs like the LS310 maintain balance and accuracy even under temperature cycling. For designers upgrading legacy systems or maintaining long-term platforms, Linear Systems’ bipolar families also serve as drop-in replacements  for many classic transistor types from Amelco, National, and Intersil. Designing with Confidence Choosing the right transistor pair often comes down to your application’s operating voltage, gain target, and thermal environment. Linear Systems offers both NPN and PNP duals  with complementary performance, making it straightforward to design push-pull amplifier stages  or balanced sensor inputs . A few design tips: Keep both transistors at the same thermal potential for best tracking. Match emitter resistances in differential applications. For ultra-low drift, pair complementary NPN and PNP devices from the same process family. Review each device’s datasheet for log conformity and beta matching specifications. Legacy of Precision — Built for the Future For over four decades, Linear Systems has specialized in high-performance discrete analog semiconductors —and their bipolar transistor line continues that legacy. As system voltages drop and performance margins tighten, these devices offer the unmatched consistency and analog fidelity  designers still rely on. If your circuit demands accuracy, low drift, and repeatable performance, Linear Systems’ matched bipolar transistors deliver a proven path to precision. Explore the full product line and datasheets: 🔗 linearsystems.com/bipolartransistors Request samples or technical support: 📧 info@linearsystems.com  | Sample Request Form

B1 Buffered Passive Preamp Few names in audio design inspire as much respect as Nelson Pass . For decades, Nelson has pushed the boundaries of amplifier and preamp design with simple, elegant circuits that deliver extraordinary sound quality. His work has shaped the way audiophiles, DIY builders, and even professional engineers think about high-end audio. One of his most enduring contributions is the B1 Buffer Preamp . At first glance, it looks deceptively simple: a unity-gain buffer with just a handful of components. But simplicity is part of the magic. The B1’s performance comes directly from the quality of the devices at its heart — JFETs , chosen for their unmatched noise and linearity characteristics. Why JFETs? JFETs are ideal for front-end and buffer applications because of their: High input impedance  – preventing loading on delicate audio sources. Low output impedance  – ensuring strong, stable drive into power amps. Low noise and excellent linearity  – crucial for preserving the subtle details in music. Nelson Pass has long relied on Linear Systems’ JFETs in this role. In the B1, the complementary pair of N-channel  and P-channel JFETs  provides transparency and neutrality — qualities that have made the circuit famous in the audio DIY community. Linear Systems Inside The classic B1 buffer used the 2SK170 and 2SJ74, but as those parts became scarce, Nelson and the DIY community turned to Linear Systems’ equivalents : LSK170  – N-channel JFET, ultra-low noise, high transconductance, widely used in audio and precision instrumentation. LSJ74  – P-channel complement, designed as a low-noise, high-performance match to the LSK170 . LSK389  – dual, monolithic version of the LSK170 , offering superb device matching and thermal tracking in a single package. By integrating these parts, the B1 achieves a combination of clarity, drive, and quiet backgrounds  that has made it a reference design for both commercial and DIY preamps. Design Philosophy: Simple but Brilliant The B1 isn’t about flashy complexity or an endless parts list. It’s about getting the fundamentals right. Nelson has often said that he prefers simple circuits with the best possible devices , and the B1 reflects that philosophy. With Linear Systems’ JFETs, the B1 offers: Musical transparency  – nothing added, nothing taken away. Reliability and stability  – thanks to tightly controlled device specifications. Enduring accessibility  – DIYers and builders around the world continue to build and enjoy this design. A Partnership Built on Trust Nelson Pass has been a longtime friend of Linear Systems , and his decision to use our JFETs reflects a deep trust in their performance and consistency. From phono stages to amplifiers to buffers like the B1, Linear Systems devices have become a staple in Pass designs. That legacy continues today, as both professional audio engineers and hobbyists choose LSK170 , LSJ74 , and LSK389  as drop-in solutions for their high-end audio projects. Learn More & Build It Yourself The full B1 Buffer schematic and project description are available directly from Nelson Pass at PassDIY – B1 Buffer. Whether you’re an audiophile, a designer, or a curious DIY builder, the B1 is a perfect example of how great devices make great circuits possible . At Linear Systems, we’re proud to see our JFETs featured at the core of such a beloved design. 🔗 View the schematic and project at PassDIY – B1 Buffer .

When designing circuits for test instrumentation , medical electronics , or any system where stable, low current is crucial, the choice of a current-regulating diode (CRD) can make all the difference. Linear Systems’ J500  and SST500  series provide engineers with reliable, tightly specified constant-current performance — even across wide voltage and temperature ranges — while simplifying circuit design. What is a Current Regulating Diode? A current-regulating diode (also called a constant current diode) is a two-terminal device that limits current to a fixed value, regardless of voltage fluctuations within its operating range. Internally, most CRDs use a JFET with the gate tied to the source. Once the device reaches saturation, the current remains steady over a wide voltage swing. This gives designers a simple, compact, and reliable current source  without additional circuitry. Key advantages: Reduced part count compared to op-amp or resistor-based current sources Stable performance across voltage changes Compact and easy to integrate in low-power and battery-driven designs The J500 & SST500 Series at a Glance Feature J500 Series SST500 Series Package TO-92 (through-hole), plus bare die SOT-23 (surface mount), plus bare die Current Range ~0.19 mA to 5.6 mA (nominal) ~0.19 mA to 5.6 mA (nominal) Operating Voltage Up to 50 V Up to 50 V Temperature Range −55 °C to +150 °C −55 °C to +150 °C Forward Capacitance ~2.2 pF (typical) ~1.5 pF (typical) 🔗 J500 Product Page 🔗 SST500 Product Page Why It Matters Tight, predictable performance  — essential for sensitive applications in medical instrumentation and precision test gear. Package flexibility  — TO-92 for prototyping and robust handling, SOT-23 for space-constrained SMT designs. High reliability  — Wide voltage and temperature ratings ensure stable performance even in harsh environments. Simplified design  — Drop-in constant current without biasing networks or active components. Application Examples Driving LEDs or photodiodes with a fixed current, even as supply voltage changes Providing a stable bias for RTDs, thermistors, or strain gauges Current sources in battery-powered medical devices Simplifying constant-current references in test and measurement equipment Choosing Between J500 & SST500 Prototyping / through-hole builds  → J500 (TO-92 package) Compact SMT designs  → SST500 (SOT-23 package, lower parasitics) Custom packaging or tighter screening  → Bare die options available directly from Linear Systems Final Thoughts Linear Systems’ J500 and SST500 current regulating diodes  deliver stable, predictable current regulation in easy-to-use packages. With options ranging from TO-92 to SOT-23 to bare die, and current levels spanning ~0.19 mA to 5.6 mA, these CRDs simplify circuit design while ensuring high performance across demanding applications. 📄 Explore datasheets on our Current Regulating Diodes page ✉️ Contact our applications team at support@linearsystems.com  for design guidance 📦 Request samples to evaluate the J500 and SST500 in your next design Prefer to speak with someone directly? Give us a call at (510) 490-9160 and our team will connect you with the right person.

Detecting the almost undetectable takes extraordinary precision. In fields from seismic monitoring to medical diagnostics, engineers often face a fundamental challenge: the signals they want to measure are buried in noise. A few picoamps of current or microvolts of voltage can hold crucial information — but only if your circuit can hear it. That’s where Linear Systems’ ultra-low noise JFETs  come in. Why JFETs Excel at Quiet Signal Detection JFETs are inherently low-noise devices, and Linear Systems’ precision-matched small-signal JFETs take that advantage even further. Parts like the LSK170  and LSK389  are designed to deliver exceptionally low gate current and noise density , making them ideal for high-impedance sensors such as: Geophones and seismometers Photodiodes and avalanche photodiodes (APDs) Ionization chambers and radiation detectors Precision strain gauges and MEMS sensors With input noise voltages measured in nanovolts per √Hz, these devices help engineers extract meaningful data where other devices see only static. Real-World Impact When paired with precision resistors and low-leakage capacitors, Linear Systems’ JFETs form the heart of front-end amplifier stages that must preserve signal integrity from the very first electron. They enable: Higher sensitivity  — Detect smaller signals without sacrificing SNR Wider dynamic range  — Maintain linearity from picoamps to milliamps Temperature stability  — Maintain accuracy in harsh or cryogenic environments Engineers worldwide rely on these JFETs to design instrumentation that can measure the imperceptible — from tracking tectonic drift to detecting a single photon. Bringing It All Together Ultra-low noise front ends start with the right transistor. Explore Linear Systems’ JFET portfolio to see how you can push your design’s sensitivity limits: 🔗 View our JFET product family 🔗 Request free engineering samples 📞 Call us at (510) 490-9160 or   📧 Email support@linearsystems.com

Precision Protection for Precision Circuits In modern high-impedance analog systems, every picoamp counts . When your front end is measuring nanoamps—or even picoamps— microamp-level diode leakage can swamp the signal , distort measurements, and silently undermine performance. That’s why designers turn to Linear Systems’ PAD and DPAD Series Low Leakage Diodes —purpose-built to deliver ultra-low reverse leakage , low junction capacitance , and exceptional thermal stability . Why Low Leakage Matters Standard silicon diodes can leak nanoamps to microamps , which becomes significant in sensor and measurement circuits. Linear Systems’ PAD and DPAD Series diodes achieve reverse leakage in the picoamp range , even across temperature extremes, helping engineers maintain accuracy and repeatability. Key benefits: ⚡ Ultra-low reverse leakage  → preserves accuracy in high-impedance circuits 📉 Low junction capacitance  → maintains bandwidth and reduces distortion ♨️ Thermally stable  → consistent performance over temperature 🛡️ Fast recovery  → protects sensitive nodes without adding error The Product Families PAD Series – Single Low Leakage Diodes Industry-leading reverse leakage in the picoamp range Ideal for guarding, clamping, or protecting single high-impedance nodes Common part numbers: PAD1, PAD2, PAD5 DPAD Series – Dual Matched Low Leakage Diodes Two matched low-leakage diodes on the same die Excellent thermal tracking and symmetry Ideal for differential sensor front ends, precision measurement bridges, and long-term stability Common part numbers: DPAD1, DPAD2, DPAD5 Where They’re Used Today Precision Measurement & Test Equipment Guard diodes and clamps in electrometers, picoammeters, and high-impedance voltage dividers Leakage-sensitive front ends in source-measure units (SMUs) and photodiode amplifiers Sensor Interfaces Protecting ADC and amplifier inputs in spectroscopy, photometry, and bio-sensing systems Limiting charge injection in capacitive or charge-redistribution sensors Low-Noise Analog & RF Systems Bias stabilization and protection in ultra-low-noise audio preamps, RF front ends, and oscillators Diode clamps in high-impedance nodes to prevent overvoltage without adding leakage Industrial & Aerospace Systems Monitoring high-resistance networks (e.g., insulation monitors) where leakage corrupts readings Long-duration missions where diode stability over decades is crucial Summary Leakage currents that were once negligible are now design-limiters. Linear Systems’ PAD and DPAD Series Low Leakage Diodes  give engineers the picoamp-level assurance  they need to build stable, accurate analog systems in today’s high-impedance designs. If your front end needs to stay quiet and accurate— start by eliminating the leakage. 👉 Request Samples Here Have technical questions, need a quote, or looking for more information? Our engineers are here to help: 📞 Call us at (510) 490-9160 or   📧 Email support@linearsystems.com

When it comes to photodiode front ends, noise and stability  are the real challenges. Photodiode capacitance can destabilize feedback loops, while input bias current and 1/f noise often dominate performance at low signal levels. Designing a transimpedance amplifier (TIA) that maintains accuracy across temperature and frequency isn’t trivial. That’s where Linear Systems’ single JFETs —the LSK170 and upcoming BF862 replacement —shine. Both provide ultra-low leakage, low noise, and high input impedance, making them ideal for photodiode buffering in precision TIAs. Why Use a JFET Front End? Many TIAs rely solely on op-amps. But at high feedback resistances— 1 MΩ and above —input bias current quickly turns into millivolts of error. A JFET buffer solves this by isolating the op-amp from the photodiode capacitance and keeping gate currents in the picoampere range . Key benefits of using LSK170 or BF862 replacement in photodiode TIAs: Ultra-low gate leakage  → minimizes dark current and DC errors. Low 1/f noise  → critical for low-frequency sensor and instrumentation applications. High input impedance  → supports large-value feedback resistors without loading effects. Bootstrapping effect  → reduces effective photodiode capacitance, improving stability and bandwidth. Example Design – Single JFET-Buffered TIA A widely used approach is to buffer the photodiode with a single JFET ( LSK170 or BF862 replacement)  before the op-amp’s inverting input. RF = 1 MΩ CF = 0.5–2 pF  (for stability compensation) Photodiode capacitance:  2–10 pF Supply: ±12 V to ±15 V This configuration provides: Gain: ~1 V/µA (1 µA photocurrent → 1 V output) Bandwidth: >100 kHz (depending on photodiode capacitance and compensation) Noise: dominated by RF’s Johnson noise, with minimal added contribution from the JFET. Bench Results In lab tests with an ~8 pF silicon photodiode and modulated LED source: Step response:  clean at 100 kHz with <10% peaking. Noise: only a few µVrms (20 Hz–100 kHz). Offset drift:  stable within millivolts from 25 °C to 60 °C. These results confirm that using a single JFET like the LSK170 or BF862 replacement  yields quiet, stable TIAs without added complexity. Applications Optical sensors  – spectrometers, fluorescence detectors, LiDAR receivers Scientific instrumentation  – low-light measurement, precision photometry Industrial monitoring  – process control, position sensing, safety systems Audio front ends  – ultra-low-noise preamps for microphones and pickups Advanced Option – Using the LSK389 Dual For most single-ended photodiode TIAs, the LSK170 or BF862 replacement  is the best choice. However, engineers needing even lower noise or matched pairs  can consider the LSK389 dual JFET : Use one half  as a drop-in replacement for a single JFET. Parallel both halves  for ~3 dB lower voltage noise (at the cost of ~2× leakage). Matched dual geometry  ensures excellent thermal tracking, ideal for differential photodiodes or ultra-stable instrumentation. Summary Photodiode TIAs demand a careful balance of speed, noise, and stability . By combining a low-noise op-amp with a Linear Systems JFET buffer , designers can achieve: Picoamp-level input bias currents Low 1/f noise Stable operation with high feedback resistors Choose your device: LSK170 / BF862 replacement  → best for single-ended TIAs, cost-sensitive designs, and wide adoption. LSK389 dual  → premium option for ultra-low drift, differential front ends, or noise-critical systems. 👉  Explore Linear Systems’ LSK170 , BF862 replacement, and LSK389 JFETs  for your next optical front-end design.

High-speed analog switching is essential in systems where signal integrity, bandwidth, and reliability cannot be compromised. Linear Systems’ DMOS High-Speed Switches  are designed to provide fast, low-distortion switching with the stability required in precision applications. Key Advantages of DMOS High-Speed Switches Fast switching speeds  – Turn-on times as low as 1 ns and turn-off times around 3 ns. Low on-resistance (RON)  – Minimizes signal loss and distortion, improving overall system accuracy. Low charge injection and low leakage  – Ensures clean signal transitions with minimal artifacts. Wide bandwidth operation  – Suitable for applications extending into RF and video frequencies. High off-isolation  – Reduces crosstalk between channels in complex switching systems. Typical Applications These characteristics make DMOS high-speed switches an excellent choice for: Video and RF routing  – Preserving signal fidelity in high-frequency paths. Data acquisition systems  – Used in multiplexers, sample-and-hold circuits, and front-end switching for A/D converters. Programmable filters and signal conditioning  – Allowing reconfigurable designs without introducing switching artifacts. Video overlay and instrumentation  – Adding signals to analog video streams cleanly, without visible distortion. Audio switching and de-glitching  – Quiet, low-distortion switching in sensitive analog audio paths. Example: SD5000 Series The SD5000 Series  from Linear Systems illustrates the advantages of this technology: Quad N-channel lateral DMOS FET switch Zener diode protection for improved reliability Pin-for-pin replacement for legacy Siliconix parts Available in PDIP, SOIC, ceramic, or as bare die for hybrid modules Screening and test options are available for applications requiring additional reliability. Summary DMOS High-Speed Switches combine low on-resistance, high speed, and low charge injection  to deliver reliable analog switching for video, RF, data acquisition, and audio systems. For engineers designing high-performance instrumentation or communication equipment, they provide a proven and stable solution where signal fidelity is critical. Want to See DMOS High Speed Switches in Action? We’re offering free samples  to qualified engineers who want to evaluate our DMOS line—or other Linear Systems parts—in their own designs. 👉 Request Your Sample Here Have technical questions, need a quote, or looking for more information? Our engineers are here to help: 📞 Call us at (510) 490-9160 or   📧 Email support@linearsystems.com

Revisiting Ray Marston’s Classic Analog Designs Through a Modern Lens In Part 4 of Ray Marston’s Op-Amp Cookbook , the spotlight turns to instrumentation and test-gear circuits—power supplies, reference generators, and low-drift amplifiers that form the backbone of precision analog design. First published in Nuts & Volts  in 2001, these designs showcase the versatility of the then-ubiquitous 741 op-amp. Today, these same circuit principles remain essential. By pairing timeless architectures with Linear Systems’ ultra-low-noise JFETs, designers can achieve cleaner signals, more stable outputs, and more efficient performance in modern applications. Classic Circuits: From Variable Supplies to Overload Protection Marston introduced a series of clever instrumentation designs, including: A variable 3–15 V power supply : Built around the 741 op-amp, with a Zener-based 3 V reference and gain control via potentiometer. A power-boosted version : Using Darlington emitter followers to deliver higher current capability. An auto-protected design : Adding automatic overload detection to safeguard both circuit and load. These simple but powerful concepts highlighted how feedback, gain control, and reference generation can be combined into reliable analog building blocks. Modern Upgrades with Linear Systems FETs Where the 741 once reigned, today’s precision circuits can benefit from Linear Systems’ advanced JFET portfolio. Design Challenge Modern Solution with Linear Systems Devices Noise and Drift Devices like the LSK170  and LSK389  deliver industry-leading low noise and thermal stability, ensuring clean and reliable voltage rails. Temperature Stability Thermally matched dual JFETs maintain consistent gain across varying conditions—critical for calibration, sensing, and test gear. Efficiency and Footprint FET-based current stages can replace bulky Darlington pairs, reducing heat dissipation and improving efficiency. Fine-Grained Control Wide IDSS binning and flexible packaging make bias networks easier to optimize for modern compact designs. A Real-World Example Imagine updating Marston’s variable power supply with a Linear Systems FET front-end : Use an LSK170  to generate a clean, stable reference input. Pair it with a precision modern op-amp for ultra-low drift regulation. Replace Darlington emitter followers with a FET-based pass element, yielding higher output current in a smaller footprint. Add smart overload protection using FET-based sensing for safe, reliable operation. The result? A compact, efficient precision supply that outperforms the original while staying true to its elegant design. Why These Designs Still Matter Fundamentals endure : The principles of feedback, reference control, and gain remain cornerstones of analog design. Versatility : Precision power supplies and test circuits are still indispensable in labs, sensing systems, and instrumentation. Performance gains : Modern JFETs unlock stability, noise reduction, and efficiency that weren’t possible when the Cookbook was first written. Closing the Cookbook As we wrap up this four-part series revisiting Ray Marston’s Op-Amp Cookbook , it’s clear that analog design remains as relevant as ever. Classic circuits provide the blueprint, but Linear Systems devices transform them into high-performance solutions for today’s designers. Whether you’re building test gear, reference supplies, or precision measurement tools, our low-noise JFETs—like the LSK170  and LSK389 —deliver the accuracy and reliability modern innovation demands. 👉 Explore our product portfolio here  and discover how Linear Systems can power your next design.

From ocean exploration to naval defense, underwater acoustics  plays a critical role in how we detect, communicate, and navigate beneath the surface. Sound travels further and faster in water than in air, making it the most effective tool for underwater sensing and communication. Whether it’s tracking submarines, mapping the ocean floor, or monitoring marine life, underwater acoustic technologies rely on one key element: precise signal amplification. At the heart of these systems are operational amplifiers (op amps)  and JFETs —components where Linear Systems  specializes in delivering unmatched precision and low-noise performance. Why Amplification Matters in Underwater Acoustics All underwater acoustic systems—whether passive  (listening for sound) or active  (emitting a signal and analyzing the response)—require one common step: amplifying the signal . Without amplification, sonar echoes would be too faint to interpret. Hydrophones wouldn’t be able to detect the subtle calls of marine life. Underwater modems couldn’t transmit reliable communication signals. That’s why every sonar, hydrophone, or acoustic modem must contain an amplifier circuit. And for decades, op amps and JFETs  have been the proven building blocks of those circuits. Applications Driving the Market Underwater acoustics encompasses a wide range of technologies: Sonobuoys  – Small, expendable sonar devices deployed from aircraft or ships for anti-submarine warfare and acoustic research. Towed Arrays  – Long cables lined with hydrophones, pulled behind submarines or ships for wide-area detection. Hydrophones  – Specialized underwater microphones used in defense, oil & gas exploration, environmental monitoring, and research. Sonar Systems  – Active detection systems emitting sound pulses to map, navigate, or locate underwater targets. Underwater Modems  – Acoustic communication systems enabling data transfer between autonomous underwater vehicles (AUVs) and control stations. Underwater Transducers  – Converters of electrical energy into acoustic signals (and vice versa) that power sonar, navigation, and communication. Each of these systems depends on precision analog circuitry  to interpret faint underwater signals. Where Linear Systems Fits In Linear Systems  manufactures ultra-low-noise JFETs, precision op amps, and high-reliability small-signal semiconductors  that are designed for demanding applications like underwater acoustics. JFETs (e.g., LSK170, LSK389, LSJ74) Ideal for front-end amplification in hydrophones and sonar systems, where ultra-low noise and high input impedance are critical. Op Amps (e.g., LS358, LS844) Deliver stable, low-distortion amplification essential for processing weak underwater signals in both defense and industrial applications. Custom Analog Solutions With decades of expertise in analog semiconductor design, Linear Systems partners with engineers developing advanced sonar, modem, and transducer systems to provide optimized component solutions. Trusted Across Industries Defense contractors, marine research institutes, oil & gas exploration firms, and communications innovators depend on high-performance underwater acoustic systems. Leading manufacturers across the U.S., Europe, and Asia are advancing the field—but all rely on one common foundation: the ability to process faint underwater signals with precision. That’s where Linear Systems parts make the difference. Explore More Whether you’re designing the next-generation sonobuoy  or developing a low-noise hydrophone array , Linear Systems’ analog semiconductor portfolio  provides the performance and reliability needed for the underwater acoustic market. 👉 Explore our full line of JFETs, op amps, and precision semiconductors  at www.linearsystems.com .

In our previous blog, we explored the practical side of Part 2—linear amplifiers and active filters—and how modern devices like the LSK389 elevate those foundational circuits. Now, let’s turn the page to Part 3  of Ray Marston’s Op‑Amp Cookbook , where he dives into oscillator and switching applications of classic op‑amps such as the 741 or 3140—timeless designs that still hum with relevance today. From 741 Oscillators to Modern Stability Part 3 guides us through using op‑amps as sinewave oscillators by arranging them as linear amplifiers with feedback through frequency-selective networks. The key is to ensure zero phase shift  and unity loop gain  at the desired frequency—conditions essential for clean and stable oscillation. The celebrated Wien‑bridge oscillator  is a prime example. Marston explains that with a symmetrically arranged R–C network (R1 = R2, C1 = C2), the bridge outputs zero phase shift at the center frequency  f0=12πRC  f_0 = \frac{1}{2\pi RC} , while the network’s gain is about ⅓. By configuring an op‑amp with a feedback gain of ~3, the circuit achieves the necessary loop gain of 1 for sustained oscillation. Elevating Oscillators with Linear Systems FETs At Linear Systems, we’re always aiming to bring timeless analog topologies into peak modern performance. Here’s how our JFETs can enhance these oscillator circuits: Low Noise & Drift Oscillators are sensitive to component noise and thermal drift—two areas where our LSK389  and LSK170  shine. Their ultra-low noise and excellent matching help preserve waveform purity and stability. Diverse Biasing Options Our LSK170 series , with its wide IDSS binning and packaging flexibility (TO‑92, SOT‑23, etc.), makes it easy to tailor bias circuits for stable gain control in Wien‑bridge designs. Higher Drive & Linearity The robustness of our FETs ensures better linear amplification, reducing distortion and enhancing harmonic fidelity in oscillator output—a boon for precision audio or sensing applications. Compact, High-Speed Feedback Compact dual FETs like the LSK389  allow tight, low-capacitance feedback implementations, ideal for high-frequency oscillator designs seeking compactness and agility. Why Classic Circuitry Still Matters Just as with Part 2, Part 3’s designs aren’t relics—they’re templates that still power modern design: Educational Clarity The Wien-bridge oscillator offers an intuitive understanding of feedback, phase, and gain—concepts crucial for analog design and control systems. Modern Circuit Building Blocks Oscillators remain essential in clock generation, modulation circuits, sensor drivers, and sound synthesis. High-Fidelity Potential Marrying these classic topologies with modern low-noise devices like LSK170 or LSK389 transforms simple analog circuits into high-performance modern solutions. Bringing the Concepts to Life Imagine swapping the traditional 741 in Marston’s Wien-bridge with an LSK170-based FET front-end  for superior noise performance, followed by a precision op-amp gain stage for clean, low-distortion oscillation. Or design a compact, high-frequency oscillator where the low capacitance of the LSK389  preserves waveform integrity while maintaining thermal matching. Final Thoughts Analog design isn’t fading—it’s transforming. Ray Marston’s Op-Amp Cookbook Part 3  offers foundational oscillator and switching designs that continue to educate, inspire, and serve critical roles in modern electronics. By integrating Linear Systems’ ultra-low noise, stable FETs, these classic circuits can perform better than ever—bridging theoretical beauty with real-world excellence. Isn’t that the analog engineer’s playbook in action? Explore our device portfolio HERE and see how Linear Systems components can elevate oscillator and switching circuits in your own designs.

A Breakthrough in Measuring Low-Level Thermal Noise In the recent ORNL technical memo, the Amplifiers Module Prototype emerges as a vital innovation. It offers a new way to measure ultra-low-level thermal noise. This prototype is not just another circuit; it's a precise front-end circuit designed for high-performance outcomes. Key Features of the Amplifiers Module Prototype This prototype incorporates several advanced technologies that enhance its performance: Dual-channel preamplifier chains : These chains are engineered with extremely low inherent noise. They provide high gain while preserving the integrity of micrometer-scale Johnson noise from RTD sensors. Differential amplifier/filter stage : This feature is essential for suppressing common-mode interference. It maximizes the fidelity of the signal, ensuring that the measurement is as accurate as possible. Autocorrelation across parallel channels : This innovative approach effectively rejects uncorrelated amplifier noise. By isolating the true thermometric signal, it enhances overall measurement reliability. Impact on Temperature Measurements 🏆 This design supports ORNL’s mission to achieve high-accuracy thermodynamic temperature measurements. The advancements made with the Amplifiers Module Prototype significantly boost the precision and reliability of Johnson Noise Thermometry. Applications of Johnson Noise Thermometry Johnson Noise Thermometry (JNT) is a powerful technique used in various fields. Some of the prominent applications include: Fundamental Research : JNT provides essential temperature measurements in fundamental physics experiments. It is especially useful where traditional thermometers fail. Cryogenics : Accurate temperature measurements are pivotal in cryogenic applications. JNT helps to maintain optimal conditions in superconductors and other materials. Material Science : Researchers utilize JNT for exploring material properties at very low temperatures. This method offers unprecedented insights into the thermal properties of new materials. Future Directions As research progresses, we can expect further advancements in the technology behind Johnson Noise Thermometry. Continuous improvements in electronic components and signal processing will likely lead to even more precise measurements. Conclusion The Amplifiers Module Prototype represents a significant leap forward in thermal noise measurement. By implementing advanced features, this innovative system ups the ante in achieving reliable temperature measurements. For those interested in further details, be sure to check the full report here . By enhancing our tools for measuring ultra-low-level thermal noise, we pave the way for breakthroughs in science and engineering. This technology is crucial for both present and future applications, supporting various disciplines with improved measurement capabilities.

If you're looking to preserve your guitar's tone over long cables or through multiple pedals, a JFET buffer  is an ideal first step. It's a simple, low-noise solution that matches the high impedance of your pickups to the rest of your signal chain. Here's how it works and how to build one. 🎛️ How It Works Input coupling and RF filter (R1, C1):  These components block DC and filter out unwanted high-frequency noise. Biasing network (R2–R6):  Sets the JFET’s operating point around half the supply voltage for optimal performance. JFET source-follower (Q1):  Provides near-unity voltage gain, incredibly high input impedance, and low output impedance. Output coupling & load (C3, R4):  Removes DC and ensures clean transitions. The common design uses JFETs like the 2N5457 , J201 , or MPF102 , and operates on a 9 V supply. 🔧 Building Tips from Stompville Use any general-purpose JFET—2N5457, J201, MPF102—with the same pinout ( stompville.co.uk , muzique.com ). Input impedance is set by R2; values up to 10 MΩ are acceptable. Bias current around 70–200 µA (via R3 and a current source bias) ensures low power draw and transparency. Adjust R1/C1 for your preferred RF cutoff—it defaults around 33 kHz at 4.7 kΩ and 470 pF ( stompville.co.uk ). 🛠 Parts List (Typical Values) Component Value Description R1 4.7 kΩ Input RF filter resistor C1 470 pF RF filter capacitor R2 680 kΩ – 2 MΩ Bias voltage divider R3 4.7 kΩ Sets JFET source-bias current R4 680 kΩ Output load R5, R6 1 MΩ each Gate-source biasing C2, C3 10–47 µF Input, output coupling Q1 JFET (2N5457 etc.) Core buffer transistor 📌 Why Use a JFET Buffer? High input impedance  protects your pickup tone. Low output impedance  drives long runs or pedal chains effectively. Zero gain  – no added coloration, just clean signal preservation. Low noise and power consumption —perfect for pedalboard integration. 🧰 Learn More & Build Yours Stompville’s guide and schematic : great step-by-step build article ( stompville.co.uk , pedalpcb.com , effectpedalkits.com , diyeffectspedals.com , circuitdiagram.co , effectpedalkits.com , muzique.com , forum.pedalpcb.com ). EffectPedalKits overview  with J113-based variant and theory ( effectpedalkits.com ). dpFX Pedals  shows a clean hand-drawn version using 2N5458 ( dpeffects.com ). Simple JFET Buffer board  from PedalPCB if you're looking for convenience ( pedalpcb.com ). 🔗 References Stompville – JFET Guitar/Instrument Buffer  (schematic image above) ( stompville.co.uk ) EffectPedalKits – JFET Buffer tutorial  ( effectpedalkits.com ) dpFX – JFET Buffer/preamp schematic  ( dpeffects.com ) PedalPCB – Simple JFET Buffer module  ( pedalpcb.com ) ✅ Ready to Build! Much of the magic lies in sourcing a good JFET and drilling a couple of biasing resistors to hit ~½ Vcc at the source.