< Back Low Leakage Diodes Introduction In circuit designs for sensor signal conditioning, the design engineer must protect the input section from over current and over voltage conditions. Op amps, ADC analog inputs, analog multiplexers, and [RS485] line receivers represent classes of devices that need protection. Often, the manufacturers of such devices specify the acceptable input range for voltage, or, in the case of an overvoltage condition, the allowable input current above which semiconductor or bonding wires may be damaged. Read More

< Back LTspice Press Release Linear Systems Mar 17, 2023 Linear Systems' JFETs in LTspice NEWS RELEASE FOR INFORMATION CONTACT: Linear Systems, Inc. Sales Department Phone: (510) 490-9160 Email: sales@linearsystems.com LTspice® Designers Now Have Access to Industry's Lowest Noise Part s FREMONT, Calif., March 3, 2020 – Linear Systems is announcing the inclusion of models for its JFET, bipolar, and small-signal MOSFETs in the LTspice® embedded library. Linear Systems' JFETs are now the primary selection option in LTspice®, and the company's other parts are also among the highest-performance options available in the simulation program's library. LTspice® is the premiere circuit simulation software, and Linear Systems' parts enable designers to create the lowest noise signal chains possible. Being included in the embedded library showcases these parts within LTspice®, making it easier for engineers to design the best possible products. Linear Systems specializes in the development and manufacture of precision, ultra-low-noise small-signal discrete components. Its parts, such as the LSK389 and LSK489, are used in highly demanding sensor systems ranging from the Large-Scale Synoptic Telescope to piezoelectric devices to sonobuoys. These parts also provide the front-end amplification for high-end test and measurement, medical, and audio equipment. SPICE models for Linear Systems' parts have been available previously, but users of LTspice® and other simulation software needed to manually add the models. Including the models in the LTspice® embedded library enables designers to use them in new designs with a simple mouse click. About Linear Systems Founded in 1987, Linear Systems is a full-service, privately-held designer and manufacturer of small-signal discrete semiconductors. The Fremont, CA-based company was founded by John H. Hall, co-founder of Intersil and founder of Micro Power Systems. Linear Systems' product line includes Ultra-Low-Noise N-Channel and P-Channel Dual and Single JFETs, High-Speed Lateral DMOS Switches, Bipolar Transistors, BIFET Amplifiers, Current-Regulating Diodes, Low-Leakage Diodes, MOSFETs, PhotoFETS, and Voltage-Controlled Resistors. Datasheets, application notes, SPICE models, and additional information can be downloaded at www.linearsystems.com. For customer service, contact Linear Systems at sales@linearsystems.com or call (510) 490-9160. LTspice® is owned by Analog Devices, Inc. For more information, please visit: [LTspice® at Analog Devices](https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html)

Linear Systems provides a wide range of JFET switches under its Improved Standard Products ® line of devices. We provide these components in an array of package types and make selections to specific electrical specifications upon request. JFET Switches Linear Systems provides a wide range of JFET switches under its Improved Standard Products ® line of devices. We provide these components in an array of package types and make selections to specific electrical specifications upon request. 2N/PN/SST4391 Series SINGLE, LOW NOISE, N-CHANNEL JFET SWITCH Read More 174DFN Series DFN PACKAGE, SINGLE P-CHANNEL JFET SWITCH Read More 2N5114 Series 2N5114 SERIES LOW ON-RESISTANCE, P-CHANNEL JFET SWITCH Read More 4391DFN Series DFN PACKAGE, SINGLE N-CHANNEL JFET SWITCH Read More LSJ/SST94 SINGLE P-CHANNEL JFET SWITCH Read More J/SST111 Series J111 SERIES LOW LEAKAGE, N-CHANNEL JFET SWITCH Read More J/SST174 Series SINGLE P-CHANNEL JFET SWITCH Read More 2N5018 Series 2N5018 SERIES LOW ON-RESISTANCE, P-CHANNEL JFET SWITCH Read More

< Back LSK489 App Note Introduction For circuits designed to work with high impedance sources, ranging from electrometers to microphone preamplifiers, the use of a low-noise, high-impedance device between the input and the op amp is needed in order to optimize performance. At first glance, one of Linear Systems’ most popular parts, the LSK389 ultra-low-noise dual JFET would appear to be a good choice for such an application. The part’s high input impedance (1 TΩ) and low noise (1 nV/√Hz at 1kHz and 2mA drain current) enables power transfer while adding almost no noise to the signal. But further examination of the LSK389’s specification shows an input capacitance of over 20pF. This will cause intermodulation distortion as the circuit’s input signal increases in frequency if the source impedance is high. This is because the JFET junction capacitances are nonlinear. This will be especially the case where common source amplifier arrangements allow the Miller effect to multiply the effective value of the gate-drain capacitance. Further, the LSK389’s input impedance will fall to a lower value as the frequency increases relative to a part with lower input capacitance. A better design choice is Linear Systems’ new offering, the LSK489. Though the LSK489 has slightly higher noise (1.5 nV/√Hz vs. 1.0 nV/√Hz) its much lower input capacitance of only 4pF means that it will maintain its high input impedance as the frequency of the input signal rises. More importantly, using the lower-capacitance LSK489 will create a circuit that is much less susceptible to intermodulation distortion than one using the LSK389. The LSK489’s lower gate-to-drain capacitance enables more effective, elegant audio circuit designs. The relatively high capacitance of the LSK389 often requires designers to use a cascode circuit to provide the ability to handle higher bandwidths without intermodulation distortion. The cascode does this by eliminating the Miller effect that can multiply the effective gate-drain capacitance and its associated nonlinear effects. However, the cascode adds complexity and noise contributed by the cascode transistors. The LSK489 is an N-channel dual low-noise, low-capacitance, tightly matched monolithic field effect transistor. It features: • 3ms transconductance at 2mA drain current • 1000 GΩ input impedance • 60V breakdown voltage • gate-drain capacitance of only 1.5pF • 4pF input capacitance • 1.5 nV/√Hz noise at 1kHz • best low-noise/low-capacitance combination in the industry • lowest input capacitance per unit gate length in the industry • lowest noise for a given gate length in the industry • tight Vgs matching at operating bias Read More

SINGLE, HIGH FREQUENCY, N-CHANNEL JFET AMPLIFIER < Back J/SST/U308 Series SINGLE, HIGH FREQUENCY, N-CHANNEL JFET AMPLIFIER The J/SST/U308 Series Single, High Frequency, N-Channel JFET Amplifier is a direct replacement for the Fairchild, NXP and Siliconix-Vishay equivalent part. It is ideal for High Frequency Applications. The series is available in the TO-92 3L RoHS, TO-18 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 series: J308 TO-92 3L RoHS J309 TO-92 3L RoHS J310 TO-92 3L RoHS U308 TO-18 3L RoHS U309 TO-18 3L RoHS U310 TO-18 3L RoHS SST308 SOT-23 3L RoHS SST309 SOT-23 3L RoHS SST310 SOT-23 3L RoHS U308 Die U309 Die U310 Die Datasheet Spice Model Application Notes

TIGHTLY MATCHED, MONOLITHIC DUAL, NPN TRANSISTOR < Back LS3250 Series - Dual TIGHTLY MATCHED, MONOLITHIC DUAL, NPN TRANSISTOR The LS3250 Tightly Matched, Monolithic Dual, NPN Transistor is a Higher Current Version of the MP310, MP311, MP312, and MP313 Series. It is ideal for Higher Current, Small Signal Transistor, Super Beta, Amplifier & Switching Applications. It is available the in TO-71 6L RoHS, TO-78 6L RoHS, PDIP 8L 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: LS3250A TO-71 6L RoHS LS3250B TO-71 6L RoHS LS3250C TO-71 6L RoHS LS3250A TO-78 6L RoHS LS3250B TO-78 6L RoHS LS3250C TO-78 6L RoHS LS3250A PDIP 8L RoHS LS3250B PDIP 8L RoHS LS3250C PDIP 8L RoHS LS3250A SOIC 8L RoHS LS3250B SOIC 8L RoHS LS3250C SOIC 8L RoHS LS3250A Die LS3250B Die LS3250C 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

N-CHANNEL JFET, VOLTAGE CONTROLLED RESISTOR < Back LS26VNS N-CHANNEL JFET, VOLTAGE CONTROLLED RESISTOR The LS26VNS N-Channel Single JFET voltage controlled resistor has a drain-source resistance that is controlled by a DC bias voltage (VGS) applied to a high impedance gate terminal. Minimum RDS of 14 Ω occurs when VGS = -1.0V. As VGS approaches the pinch-off voltage of -6.0V RDS rapidly increases to the maximum value or RDS = 38 Ω. For the P-Channel version, please see our LS26VPS. Both the N and P-channel parts are made from the same die geometry, making them complimentary. This part is available in the TO-92 3L RoHS, SOT-23 3L RoHS and DFN 8L 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: LS26VNS TO-92 3L RoHS LS26VNS SOT-23 3L RoHS LS26VNS DFN 8L RoHS Datasheet Spice Model Application Notes

Linear Systems’ low-leakage diodes provide a superior alternative to conventional diode technology when reverse current must be minimized. These devices are well suited for use in applications such as input protection for operational amplifiers. Low Leakage Diodes Linear Systems’ low-leakage diodes provide a superior alternative to conventional diode technology when reverse current must be minimized. These devices are well suited for use in applications such as input protection for operational amplifiers. J/SST/PAD Series SINGLE, LOW LEAKAGE PICO-AMP DIODES Read More ID100 Series MONOLITHIC DUAL, PICO AMP LOW LEAKAGE DIODES Read More PAD Series DFN Package SINGLE, LOW-LEAKAGE PICO AMP DIODES DFN PACKAGE Read More DPAD/SSTDPAD Series LOW LEAKAGE, MONOLITHIC DUAL, PICO-AMP DIODE Read More

< Back App Note by Dimitri Danyuk Linear Systems Mar 17, 2023 Headphone Amplifier Evaluation Board 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

< Back CMR Ratio in Dual JFETs Introduction When choosing the optimal JFET for a new circuit, a characteristic often overlooked is how the part’s design affects the rejection of unwanted inputs while amplifying the signal as accurately as possible. Single JFETs provide excellent impedance matching and low-noise amplification, but lack one important quality of their dual counterparts – dual discrete devices largely reject common signals. This important characteristic – Common Mode Rejection – means that selecting the right dual JFET can be the most cost-effective way of improving signal-to-noise ratio in a design. 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