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< Back Consider the JFET Introduction Though not as well known as the bipolar transistor or op amp, this long-established transistor still excels in where you need to optimize circuit behavior, such as for lowest noise. Many engineers are somewhat familiar with discrete bipolar transistors, such as the venerable 2N2222. They are also comfortable with the MOSFET (metal-oxide semiconductor field-effect transistor) as a discrete device for amplifying analog signals and switching power signals, as well as its role as the key digital structural element in large-scale ICs. But alongside these devices is the JFET (junction field-effect transistor), which was developed soon after the bipolar transistor. To many designers, the JFET is the nearly ideal three-terminal solid-state device, and its operation and parameters are analogous to the vacuum-tube triode. The difference is that the JFET is, of course, a low-voltage, much-more efficient device, although it can't deliver the power that a vacuum tube can. For applications which require extremely low noise, the JFET is often offers superior performance compared to any other discrete device, as well as op amps. Read More

< Back Design Specs for JFETs Introduction Junction field effect transistors (JFETs) are used and are useful in many different circuit topologies. Because these devices function as voltage controlled current sources (VCCS) as opposed to current controlled current sources (CCCS), they offer designers certain flexibilities in designs not available when using bipolar transistors (which are CCCS devices). JFETs can also be used as voltage controlled variable resistors and voltage-controlled switches. JFETs have extremely high input impedances (on the order of giga-ohms) and extremely low input leakage currents (on the order of pico-amps). Selected parts are designed to have excellent performance in high and very high frequency (VHF) circuits. Read More

HIGH INPUT IMPEDANCE, N-CHANNEL JFET AMPLIFIER < Back LS5301 HIGH INPUT IMPEDANCE, N-CHANNEL JFET AMPLIFIER The LS/PF/SST5301 Series Single, High Input Impedance, N-Channel JFET Amplifier is a direct replacement for the Fairchild equivalent part. It is ideal for Very High Input Impedance Applications. Available in TO-72 4L RoHS, TO-92 3L RoHS and SOT-23 3L RoHS package, as well as in die form. Advanced screening options are available for our diverse product lineup, featuring JFETS, Bipolar transistors, MOSFETs, current regulators, and Diodes. Our special screening covers all the parameters listed in the standard datasheet, including comprehensive package pin-out. Connect with our experienced technical team to discuss your specific needs and tailor your requirements—email us at support@linearsystems.com or call (510) 490-9160. MOQ applies to these specialized services. Ordering Information Below are the options you have when ordering this part: PF5301 TO-92 3L RoHS LS5301 TO-72 4L RoHS SST5301 SOT-23 3L RoHS LS5301 Die Datasheet Spice Model Application Notes

Linear Systems designs and manufactures the highest-performance line of monolithic dual JFETs in the industry. Contact us for a quote! Back LS840 Series LOW-NOISE, LOW-DRIFT, LOW CAPACITANCE, MONOLITHIC DUAL N-CHANNEL JFET AMPLIFIER The LS840 Series Low-Noise, Low-Drift, Low-Capacitance, Monolithic Dual N-Channel JFET Amplifier is a pin-for-pin replacement for the Fairchild, Motorola, National and Siliconix-Vishay part series. Available in the TO-71 6L, TO-78 6L, PDIP 8L and SOIC 8L RoHS package, as well as bare die. Advanced screening options are available for our diverse product lineup, featuring JFETS, Bipolar transistors, MOSFETs, current regulators, and Diodes. Our special screening covers all the parameters listed in the standard datasheet, including comprehensive package pin-out. Connect with our experienced technical team to discuss your specific needs and tailor your requirements—email us at support@linearsystems.com or call (510) 490-9160. MOQ applies to these specialized services. Ordering Information Below are the options you have when ordering this part series: LS840 TO-71 6L RoHS LS841 TO-71 6L RoHS LS842 TO-71 6L RoHS LS840 TO-78 6L RoHS LS841 TO-78 6L RoHS LS842 TO-78 6L RoHS LS840 PDIP 8L RoHS LS841 PDIP 8L RoHS LS842 PDIP 8L RoHS LS840 SOIC 8L RoHS LS841 SOIC 8L RoHS LS842 SOIC 8L RoHS LS840 Die LS841 Die LS842 Die Datasheet Spice Model Application Notes

SINGLE, LOW-LEAKAGE PICO AMP DIODES DFN PACKAGE < Back PAD Series DFN Package PAD-DFN SERIES MINIATURE/NON MAGNETIC 8-PIN DFN PACKAGE LOW LEAKAGE DIODE PAD Series Ultra-Low Leakage Protection Diodes (Picoamp Level) The PAD Series ultra-low leakage protection diodes from Linear Systems are precision devices designed for circuits requiring picoamp-level leakage performance , high stability, and reliable signal protection. These diodes serve as direct drop-in replacements for the Siliconix-Vishay PAD series , making them ideal for legacy designs, upgrades, and new precision analog applications. Engineered for ultra-low current environments, the PAD Series is widely used in high-sensitivity measurement circuits, instrumentation front ends, and precision sensing systems where leakage current directly affects accuracy. Available in multiple industry-standard, RoHS-compliant packages — DFN-8L, TO-72, TO-92, SOT-23, and bare die — the series supports flexible PCB layouts and assembly processes across commercial, industrial, and scientific designs. Key Features Ultra-low leakage current (picoamp range) Direct replacement for Siliconix/Vishay PAD devices High stability for precision analog circuits Multiple package options including surface-mount and through-hole Available as packaged devices or bare die RoHS compliant Applications The PAD Series is ideal for ultra-low current protection and measurement circuits , including: electrometers photodiode protection circuits precision instrumentation medical sensing equipment charge amplifiers low-current measurement front ends scientific and laboratory instruments Advanced Screening Options Linear Systems offers custom screening and parameter selection across our product portfolio — including JFETs, bipolar transistors, MOSFETs, current regulators, and diodes — for applications requiring enhanced performance, tighter limits, or reliability assurance. Screening can be performed on any datasheet parameter and includes full package pin-out verification. Contact our technical team to discuss requirements: support@linearsystems.com 📞 (510) 490-9160 Minimum order quantities apply for specialized screening services. Ordering Options Package Available Part Numbers DFN-8L (RoHS) PAD5, PAD10, PAD20, PAD50, PAD100 TO-72 (3L, RoHS) PAD1, PAD2, PAD5, PAD10, PAD20, PAD50, PAD100 TO-92 (2L, RoHS) — JPAD Series JPAD5, JPAD10, JPAD20, JPAD50, JPAD100 SOT-23 (3L, RoHS) PAD5, PAD10, PAD20, PAD50, PAD100 Bare Die PAD1, PAD2, PAD5, PAD10, PAD20, PAD50, PAD100 Datasheet Spice Model Application Notes

< Back FETching Discrete Amplifier Introduction Low-noise amplifiers for photodiode, piezoelectric, and other instrumentation applications typically call for circuit parameters such as extremely high input impedance, low 1/f noise, or subpicoamp bias currents that cannot be met with available integrated products. This article discusses the requirements and challenges of designing a low-noise amplifier using discrete components, with particular emphasis on input-referred noise and offset voltage trimming. Read More

Linear Systems designs and manufactures the highest-performance line of monolithic dual JFETs in the industry. Contact us for a quote! Back 2N/LS5905 Series LOW-LEAKAGE, LOW-DRIFT, MONOLITHIC DUAL, N-CHANNEL JFET AMPLIFIER The 2N/LS5905 Series Low Leakage, Low Drift, Monolithic Dual N-Channel JFET Amplifier features tight matching and low drift over temperature specifications. The series is targeted for use in a wide range of precision instrumentation applications where tight tracking is required. Linear Systems’ version of this part series is a direct, pin-for-pin replacement of the Intersil part. Available in the TO-78 7L RoHS and SOIC 8L RoHS package, as well as bare die. Advanced screening options are available for our diverse product lineup, featuring JFETS, Bipolar transistors, MOSFETs, current regulators, and Diodes. Our special screening covers all the parameters listed in the standard datasheet, including comprehensive package pin-out. Connect with our experienced technical team to discuss your specific needs and tailor your requirements—email us at support@linearsystems.com or call (510) 490-9160. MOQ applies to these specialized services. Ordering Information Below are the options you have when ordering this part series: LS5905 TO-78 7L RoHS LS5906 TO-78 7L RoHS LS5907 TO-78 7L RoHS LS5908 TO-78 7L RoHS LS5909 TO-78 7L RoHS 2N5905 TO-78 7L RoHS 2N5906 TO-78 7L RoHS 2N5907 TO-78 7L RoHS 2N5908 TO-78 7L RoHS 2N5909 TO-78 7L RoHS LS5905 SOIC 8L RoHS LS5906 SOIC 8L RoHS LS5907 SOIC 8L RoHS LS5908 SOIC 8L RoHS LS5909 SOIC 8L RoHS Datasheet Spice Model Application Notes

LOW NOISE N-CHANNEL JFET GENERAL PURPOSE AMPLIFIER < Back J/SST210 Series LOW NOISE N-CHANNEL JFET GENERAL PURPOSE AMPLIFIER The J/SST210 Series Single, Low Noise, N-Channel JFET, General Purpose Amplifier is a direct replacement for Fairchild, NXP and Siliconix-Vishay equivalent part. It is ideal for General Purpose and Low Noise Applications. Available in the TO-92 3L RoHS, SOT-23 3L RoHS package, as well as die form. Advanced screening options are available for our diverse product lineup, featuring JFETS, Bipolar transistors, MOSFETs, current regulators, and Diodes. Our special screening covers all the parameters listed in the standard datasheet, including comprehensive package pin-out. Connect with our experienced technical team to discuss your specific needs and tailor your requirements—email us at support@linearsystems.com or call (510) 490-9160. MOQ applies to these specialized services. Ordering Information Below are the options you have when ordering this part series: J210 TO-92 3L RoHS J211 TO-92 3L RoHS J212 TO-92 3L RoHS SST210 SOT-23 3L RoHS SST211 SOT-23 3L RoHS SST212 SOT-23 3L RoHS J210 Die J211 Die J212 Die Datasheet Spice Model Application Notes

SINGLE, P-CHANNEL ENHANCEMENT MODE MOSFET < Back 3N163 Series SINGLE, P-CHANNEL ENHANCEMENT MODE MOSFET The 3N163 Series Single, P-Channel Enhancement Mode MOSFET is a direct replacement for Intersil and Siliconix-Vishay equivalent part. It is ideal for Amplifier and switching Applications. This part series is available in the TO-72 4L RoHS and SOT-143 4L RoHS package, as well as bare die. All Linear Systems devices are available with special testing to customer specifications. Ordering Information Below are the options you have when ordering this part series: 3N163 TO-72 4L RoHS 3N164 TO-72 4L RoHS 3N163 SOT-143 4L RoHS 3N164 SOT-143 4L RoHS 3N163 Die 3N164 Die Datasheet Spice Model Application Notes

< Back Solving the Noise Puzzle Introduction Noise is one of the more important aspects of circuit design. Lower noise in audio amplifier design means better quality audio. Low-noise in instrument design means more reliable and accurate measurements at lower voltage and current levels. And low-noise in current source designs means less noise injected into the electronic system. One of the most basic approaches to reduce noise in an amplifier is to use low-noise components. This would include low-noise bipolar transistors and low-valued resistors. Although one can use low-noise operational amplifiers in the design of low-noise circuits or low-noise current sources it is often not done. This is because lower noise can be often be obtained with a well-thought out discrete design. And that’s because discrete transistors offer much more design customization capability for specific circuit applications – like optimized collector biasing. One must remember that monolithic chip designs are built for the most part for general purpose applications. It is hard to tailor a specific op amp or current source chip for a specific source resistance, specific power consumption requirement and a specific bandwidth that will lower the overall noise – that is unless you add-on more compensation components. Read More

< Back JFETs for VC Circuits Introduction Linear Integrated Systems manufactures a variety of FETs (Field Effect Transistors). In particular they have a variety of matched dual products. There are advantages in having matched devices. For example, if you are building a twochannel stereo audio product, having two or four devices in the same package allows for the two audio channels to be more closely matched. This paper will explore using FETs in voltage controlled circuits. Several approaches will be shown: 1. Using FETs as voltage controlled resistors. 2. Using FETs as voltage controlled amplifiers and active mixers. 3. Using FETs as voltage controlled phase shifters for processing music. 4. Using FETs as voltage controlled band pass filters. We will also explore ways to reduce nonlinearities or distortions and automatically bias the FETs. Read More

ULTRA LOW NOISE, HIGH IDSS SINGLE N-CHANNEL JFET AMPLIFIER < Back LSK170X ULTRA LOW NOISE, HIGH IDSS SINGLE N-CHANNEL JFET AMPLIFIER The LSK170X Ultra Low-Noise, High Idss, Single N-Channel JFET Amplifier is ideal for Ultra-Low Noise Audio/Acoustic Applications. Available in the TO-92 3L RoHS, SOT-23 3L RoHS and SOT-89 3L RoHS package, as well as in die form. Advanced screening options are available for our diverse product lineup, featuring JFETS, Bipolar transistors, MOSFETs, current regulators, and Diodes. Our special screening covers all the parameters listed in the standard datasheet, including comprehensive package pin-out. Connect with our experienced technical team to discuss your specific needs and tailor your requirements—email us at support@linearsystems.com or call (510) 490-9160. MOQ applies to these specialized services. Ordering Information Below are the options you have when ordering this part series: LSK170X TO-92 3L RoHS LSK170X SOT-23 3L RoHS LSK170X SOT-89 3L RoHS LSK170X Die Datasheet Spice Model Application Notes