Pro Audio Design Forum

Linear Systems has announced the dual P Channel LSJ689 compliment to the LSK489.

Historically, P-Channel JFETs availability has declined. Complementary Single N-Channel and P-Channel JFETs have become limited to a few industry standards. Complementary monolithic dual N-Channel and P-Channel JFETs have not been offered for many years, leaving designers under supported. In response, LIS produced Single Complementary N & P Channel JFETs, the LSK170 and LSJ74 family. The LSJ689 and LSK489 provide additional options for designers. The LSJ689/LSK489 have 1/5 the capacitance of the LSK170 and LSJ74, 4pF versus 25pF. A unique Monolithic Dual design construction of interweaving each JFET on the same piece of silicon provide excellent matching and thermal tracking.

When used together, the LSJ689 and LSK489 are ideal for differential input stages for amplifier, phono, and preamplifier designs. Additional applications for the LSJ689 include voltage controlled resistors, thermal stable source followers, sample and hold, and current matched sources.

Summary of Features:

Complement to the Ultra Low Noise Monolithic Dual N-Channel JFET LSK489
Ultra Low noise (typically 1.8 nV/Hz @ 1kHz)
Nearly zero popcorn noise
Idss (drain-source saturation current) matching to 10% max
Low offset/tight matching (|Vgs1- Vgs2| = 20mV max)
Low capacitance (Ciss=4 pF)
High input impedance
High breakdown voltage (BVGSS = 40V Min)
Monolithic Dual (2 JFETS on one piece of silicon, better matching and thermal tracking)
Surface mount SOIC-A 8L versions and the smaller SOT-23 6L package
Lead-free/ROHS compliant

LSJ689 Data Sheet: http://www.linearsystems.com/assets/med ... 89part.pdf

Linear Systems Transistors are available in the US from Trendsetter: https://www.trendsetter.com/Transistors-s/23000.htm
LSJ689: http://www.trendsetter.com/product-p/ls ... 1%206l.htm

The metal package shows what looks like body diodes to a common substrate but does not bring that substrate out to a pin even though they could in the 8 pin package. Substrate may be bonded to metal can in that package.

I suspect this means some gate to gate capacitance but probably modest.

I recall getting tripped up by substrate diodes in old transistor arrays if not careful.

JR