With Toshiba 2SJ74 and 2SK170 getting harder to find, are there any easily obtainable lower-noise JFET amplifier parts being made today? I know about Linear Systems but they're also spotty to get and expensive. Anything else out there that may not be as quiet as the Toshiba's but offer similar performance in most other parameters (capacitance, etc.) and not so expensive? Thanks.
BF862 is excellent N junction JFET. Now at end of life but very inexpensive and no fakes (yet). Stock up while you can. Work with N JFET only designs and couple with BJTs for higher voltage via cascoding.
The BF862 was a lucky find for an audio transistor. Very high gain; fairly low capacitances; and low noise. The low noise was a surprising gift. The device was intended for, and spec'd for, preamplifiers in the MF to HF range. A JFET that is low noise at RF frequencies isn't necessarily low noise at audio frequencies. Unfortunately there was never anything like a complementary device for the BF862.
Now that the BF862 is fading into history I'm looking at some devices from ON Semiconductor. The 2SK2394, 2SK3557, 2SK932 and CPH3910 are also specified for HF front end applications, and they share the general characteristics of the BF862. They are also available as packaged duals. I haven't found any measured data about their noise performance in audio applications, so it's hard to say whether they should be considered as substitutes for the BF862 (or 2SK170). Since these devices are so similar in characteristics I can't imagine that ON Semi would continue to produce all of them over the long term.
There may be other devices from other manufacturers. Look for high gain, low noise devices intended for use in RF amplifiers. Then, some measurements will be required to confirm low noise operation down to audio frequencies.
Dale
Measurements Rate SMT Low-Voltage n-JFETs Under Consistent Conditions | Electronic Design
I never consider BF862 as a replacement for 2SK170 or other Toshiba JFETs.
As a JFET it has very high gate currents under certain conditions.
And for me at least, it should not be used for any Vds > 5V.
PS
I do not consider LS JFETs to be 1:1 equivalent to Toshiba either.
Patrick
I never consider BF862 as a replacement for 2SK170 or other Toshiba JFETs.
As a JFET it has very high gate currents under certain conditions.
And for me at least, it should not be used for any Vds > 5V.
PS
I do not consider LS JFETs to be 1:1 equivalent to Toshiba either.
Patrick
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and now 2SK932 is end of life! Whats the world coming to?
2SK3557 is perhaps the next best alternative to BF862, so lets hope it finds reason in life and lives on.
(The LS JFETs are not pin compatible so not true replacements for BF862)
2SK3557 is perhaps the next best alternative to BF862, so lets hope it finds reason in life and lives on.
(The LS JFETs are not pin compatible so not true replacements for BF862)
I like the On Semiconductor J113/J175 pair, not an exact replacement but close enough for amplifiers, a little more noise than the Toshiba so not great for Moving coil preamps.
Just in case anyone's missed it, the new JFE150: Ultra Low Noise JFETs from Texas Instruments
Which reminds me I was going to try one of my two samples of this device out...
Which reminds me I was going to try one of my two samples of this device out...