Elegant analog design often comes down to simplicity. This 4–20 mA current-sense circuit shows how a single JFET can do the job with minimal parts. "Sometimes the simplest solution is the best. Using a single N channel JFET as a current sink, a 4-20mA instrument monitor loop can be read with a minimum of components. A 2N4392 diverts a current of 4mA until the load circuit voltage exceeds the Zener threshold where the remaining current up to 20 mA is diverted giving a linear indication from...

Many widely used ADI op-amps are excellent building blocks-but pairing them with a discrete JFET input stage can unlock lower noise, higher input impedance, and more design flexibility , especially for high-Z sensors and precision analog front ends. Where discrete JFETs shine:   • Reduce input current noise and 1/f noise • Improve performance with high-impedance sources • Allow custom gain, bandwidth, and linearity tuning • Enable better thermal tracking and matching Designers are...

Community Design Spotlight 🔍 WSF Amplifier “The Watt Sucking Fireball  amplifier illustrates a wide use range of Linear Systems  JFETs and matched bipolar transistors. It has an all JFET front end using a (Differential-Cascode-Transimpedance)™ amp driving a resistor loaded differential current to voltage gate driver; a lot to say in one sentence. Though simple in overall design concept, the goal of this design was to prove out an all N-channel JFET amplifier having almost no intermodulation...