top of page
Engineering Insights from Linear Systems
For nearly four decades, Linear Systems has specialized in high-performance discrete semiconductors for demanding analog applications. Today, we're putting that experience to work beyond the devices themselves by sharing practical technical resources for the engineering community.
Explore the Linear Systems Learning Series, JFET circuit and design spotlights, application insights, technical articles, new product releases, and semiconductor industry updates—all focused on helping engineers solve real-world analog design challenges.
You'll also find the latest on our ultra-low-noise JFETs, lateral DMOS switches, bipolar transistors, BIFETs, current regulators, low-leakage diodes, and other precision semiconductor technologies.
Subscribe to stay connected.
Get our latest technical articles, design insights, product updates, application resources, and company news delivered directly to your inbox.
Sign up below!
Search
All Posts
BEYOND “RADIATION TESTED”: WHAT NASA’S LSK389 AND LSK489 RESULTS ACTUALLY PROVE
Saying that a semiconductor has been “radiation tested” sounds definitive. It is not. Radiation test results are meaningful only when they are connected to the device samples, radiation source, accumulated dose, particle energy, operating bias, temperature, packaging, monitored parameters and intended application. NASA tested Linear Systems’ LSK389 and LSK489 dual N-channel JFETs for a specific reason: to evaluate their suitability for the Ocean Color Instrument, or OCI, deve
Oct 26
UNDERSTANDING JFET BREAKDOWN RATINGS: WHAT BVGSS AND ABSOLUTE MAXIMUM RATINGS REALLY MEAN
A JFET datasheet may list a high gate-to-source breakdown voltage—but that does not mean the device should normally operate at that voltage. Breakdown ratings, electrical specifications and absolute maximum ratings describe different boundaries. Confusing them can expose a JFET to excessive junction current, transient stress or long-term reliability problems. Understanding those distinctions is especially important in high-impedance circuits, where protection must be added wi
Oct 26
MORE THAN A FOOTPRINT: HOW PACKAGING AFFECTS PRECISION ANALOG PERFORMANCE
When engineers compare semiconductor packages, the conversation often begins with board space, assembly method and availability. But a package is more than a mechanical enclosure. It becomes part of the electrical, thermal and physical environment surrounding the semiconductor die. Its leads, bond wires, internal connections, molding materials and exposed surfaces can all influence how a precision analog circuit performs. At low frequencies and moderate impedances, these effe
Oct 26
UNDERSTANDING OUTPUT CONDUCTANCE: WHY JFET DRAIN CURRENT IS NOT PERFECTLY CONSTANT
A JFET is often described as a voltage-controlled current source. That description is useful—but it is not perfect. Once a JFET is operating beyond the knee of its output characteristic, drain current becomes much less sensitive to drain-to-source voltage. However, the current does not become completely independent of VDS. The output curves retain a finite slope. That slope is described by output conductance, commonly written as gos. Understanding gos helps engineers predict
Oct 26
THE HIDDEN DECISION IN EVERY JFET CIRCUIT: SETTING THE OPERATING POINT
The same JFET can deliver excellent performance in one circuit—and disappoint in another. The difference may not be the device itself. It may be the operating point. A JFET’s datasheet describes what the device can do under specified conditions. Biasing determines the drain current, terminal voltages and signal headroom it will actually have in the circuit. That operating point influences nearly every important aspect of performance: Gain Noise Transconductance Linearity Outp
Oct 23
SAME JFET, DIFFERENT JOB: SOURCE FOLLOWER VS. COMMON-SOURCE AMPLIFIERS
A JFET can serve very different purposes depending on how it is connected. Place the output at the drain, and the device can provide voltage gain. Take the output from the source, and the same JFET can buffer a signal while presenting a lower impedance to the next stage. These two fundamental configurations—the common-source amplifier and the source follower—appear throughout low-noise preamplifiers, sensor interfaces, audio circuits, instrumentation and other precision analo
Oct 16
Inside Burning Amp 2026: Celebrating DIY Audio & Engineering Innovation!
What happens when passionate audio enthusiasts, talented engineers, and creative builders come together? Some truly fascinating conversations! Linear Systems' Paul Norton attended Burning Amp 2026, connecting with members of the DIY audio community to learn about their projects, innovative designs, and passion for high-performance sound. From custom speaker systems and amplifiers to inventive audio electronics, these conversations highlight the creativity, technical expertise
Oct 14
JFET Design Spotlight: Keeping It Simple Whenever We Can
Sometimes the most effective analog solutions are also the simplest. This design demonstrates how a low-noise, high-gain differential amplifier can deliver excellent linearity, wide bandwidth, and fast transient response without feedback. “The sensing and manipulation of differential signals can take on a myriad of configurations using all types of semiconductor types and vacuum tubes. Inputs have all ranges of impedances, all ranges of source loading conditions, and what b
Oct 14
Linear Systems Learning Series: Understanding Gate Leakage
When engineers evaluate a JFET, specifications such as noise, transconductance, input capacitance, and IDSS often receive most of the attention. But in high-impedance circuits, another specification can become extremely important: gate leakage current. JFET gate current may be extraordinarily small, often measured in picoamps or nanoamps. But when that tiny current interacts with a very high source impedance, it can create a measurable error. Understanding gate leakage, and t
Oct 6
THE OTHER HALF OF THE SIGNAL: WHY COMPLEMENTARY JFETS MATTER
Most discussions about JFETs focus on N-channel devices. That makes sense. N-channel JFETs are widely used in low-noise amplifiers, sensor interfaces, instrumentation inputs and professional audio equipment. But N-channel devices represent only one side of what is possible. When N-channel and P-channel JFETs are used together, designers can build complementary circuit stages that handle signals more symmetrically, simplify biasing, improve drive capability and enable architec
Sep 30
BEYOND THE DATASHEET: HOW JFET NOISE IS MEASURED—AND WHY TESTING MATTERS
A JFET datasheet may list an impressively low voltage-noise number—but how was that number measured, at what frequency, and does it represent a typical value or a guaranteed maximum? Those details matter. At nanovolt-per-root-hertz levels, the measurement system, test conditions and specification method can significantly influence the result. Understanding what sits behind the published number helps engineers make more meaningful comparisons between devices. WHAT DOES A JFET
Sep 25
JFET Design Spotlight: Negative Resistance in a Semiconductor
JFETs are commonly used in amplifiers, current sources, variable resistors, and oscillators, but sometimes the most interesting designs come from using them in ways you wouldn’t normally expect. This week’s Design Spotlight explores one of those “odd uses”: creating a negative resistance effect with complementary N-channel and P-channel JFETs. “Use of JFETs in typical applications range from amplifiers to variable resistors and oscillators, among many other applications, bu
Sep 24
SD5400 Now Available in QFN 16L Package
More design flexibility. Less board space. Linear Systems has expanded the SD5400 quad analog switch family with a new compact 3 × 3 mm QFN-16 package—giving designers another surface-mount option for space-constrained, high-speed analog applications. The SD5400 integrates four independent, bidirectional SPST switches on a common substrate. Built using our proprietary lateral DMOS process, it combines low on-resistance, low interelectrode capacitance and exceptionally fast sw
Sep 23
JFET Design Spotlight: Another Variation of a High Z Preamp for Low Level Piezo Sensing
This week’s Design Spotlight is another great example of how JFETs and precision discrete components can come together to solve demanding analog design challenges. “Though there was another Piezo sensor earlier, this one has a bit more gain and a design bandwidth of 1.3 MHz. This circuit uses, as you’d expect, a low noise LSK389 differential JFET pair cascoded by Q1 & Q2 into a Widlar style current mirror. The LS310 transistor pair maintains constant voltage, low impedance
Sep 18
JFET Design Spotlight: A case for Paralleling JFETs for lower noise
What happens when you rethink low-noise amplifier design from a clean sheet? This design explores paralleling LSK389 JFETs to push noise even lower. “Things happen while throwing out historical habits in favor of a clean piece of paper. Differential Amplifiers, being relatively commonplace in analog circuit design, have traditionally followed familiar circuit practices regarding noise. For this discussion JFETs are of interest though Bipolar parts similarly apply. Front end n
Sep 16
JFET Design Spotlight: High-Speed Sonar Front End for Aquatic Imaging
This week’s Design Spotlight takes us into a sonar application proposed for multi-channel aquatic imaging. The design uses a dual matched JFET front end to meet the sensor’s differential loading requirements while providing the low-noise, high-speed performance needed for downstream A/D conversion. “Just another JFET circuit that was composed and built for a Sonar application, proposed to be used in multiple for aquatic imaging. One of the requirements was a loading impedance
Sep 4
Linear Systems Learning Series: Understanding VGS(off) - What JFET Cutoff Voltage Really Means
Last week, we looked at IDSS—the drain current a JFET conducts when VGS = 0 V under specified conditions. This week, we're looking at the other end of the JFET's transfer characteristic: VGS(off), or gate-to-source cutoff voltage. If IDSS helps tell us where the JFET starts at zero gate bias, VGS(off) helps define the point at which the channel is essentially turned off. Understanding both gives engineers a much better picture of how a JFET responds to gate voltage—and how to
Sep 2
Linear Systems Learning Series Understanding: IDSS - What Drain Current Tells You About a JFET
Last week, we took a closer look at transconductance (gfs) and what it tells engineers about how strongly a JFET responds to a change in gate voltage. This week, we're continuing our look at key JFET datasheet parameters with another specification you'll see frequently: IDSS — Drain-to-Source Saturation Current. IDSS is one of the fundamental characteristics of a JFET, and understanding it is important when selecting a device and establishing its operating point. Put simply:
Aug 26
Design Spotlight: JFET Current Limiters for the Masses
Bidirectional current limiting presents an interesting analog design challenge—and the unique structure of a JFET offers some creative ways to solve it. In this Design Spotlight, three approaches are explored, from dual-device configurations to a particularly simple single-JFET solution that takes advantage of the interchangeability of the Source and Drain. The designs highlight differences in crossover behavior, current stability, and voltage compliance, including considerat
Aug 19
Linear Systems Learning Series: Understanding Transconductance: What gfs Tells You About a JFET
Last week, we looked at how to read a JFET datasheet and the key specifications engineers should evaluate when selecting a device. This week, we're taking a closer look at one of those parameters: transconductance (gfs). Transconductance is an important JFET characteristic because it tells us how effectively the device converts a change in gate-to-source voltage into a change in drain current. Put simply: How strongly does the JFET respond to a change at its input? What Is Tr
Aug 18
bottom of page