JFETs are by bane of existence. I work with older audio gear, or gear specifically designed to have specific characteristic distortion profiles. I match JFETs rigorously to then place them in parallel. The common one for now is the Toshiba 2SK209GR. It's far underpowered for audio, hence we put them in parallel when matched!
I’m an electronics newbie. I’ve been copying the work of others to make regenerative radio receivers. The simpler circuits use a single JFET as both the RF amplifier and the audio demodulator. Amazing performance. Brilliantly clever idea. Credit to Edwin Armstrong who patented the discovery around 1915 (but using a thermionic valve where we can now use a JFET)
On the subject of MOSFETS having infinite gate impedance, and IGBTs for that matter. I often find that there is a series resistor of around 100 Ohms or so, put in series with the gate, particularly on power devices. Should the device go short circuit, the small resistance prevents destruction of the circuitry, PCB tracks and wiring connected to the gate. I service and repair welders, and there's usually a resistor in the gate connection for that reason.
i repaired a Fluke 8520A some time ago and it had a lot of JFETs they used them as switches if i remember correctly some JFETs was broken on it but the problem was i couldn't find any datasheet for them seems like they were in aircrafts for military etc so had to test a bunch of JFETs until it read right on the display lol
Sorry, Don't know. Can I measure that using another multimeter across it in millivolts range or would that in itself affect the reading? Hmmm I guess there is only one way to find out...
I haven't played with a JFET for a couple of decades now, so many thanks for the reminders. They are really useful devices.
Perfect blend of theory, practical and curiosity 👍
Thanks 🙂
JFETs are by bane of existence. I work with older audio gear, or gear specifically designed to have specific characteristic distortion profiles. I match JFETs rigorously to then place them in parallel. The common one for now is the Toshiba 2SK209GR. It's far underpowered for audio, hence we put them in parallel when matched!
My dream woman... 🤣🤣😉
@@mattstroker3742 Hah, why? Why's that? 😅😅
I never fail to learn something from one of your videos, thank you!
I’m an electronics newbie. I’ve been copying the work of others to make regenerative radio receivers. The simpler circuits use a single JFET as both the RF amplifier and the audio demodulator. Amazing performance. Brilliantly clever idea. Credit to Edwin Armstrong who patented the discovery around 1915 (but using a thermionic valve where we can now use a JFET)
Excellent!!
Great video, thank you for sharing
On the subject of MOSFETS having infinite gate impedance, and IGBTs for that matter. I often find that there is a series resistor of around 100 Ohms or so, put in series with the gate, particularly on power devices.
Should the device go short circuit, the small resistance prevents destruction of the circuitry, PCB tracks and wiring connected to the gate.
I service and repair welders, and there's usually a resistor in the gate connection for that reason.
Great explanation, Thank you. Paul, USA!
And thank you for the compliment
They are also often integrated inside of microphones or as first stage amp.
i repaired a Fluke 8520A some time ago and it had a lot of JFETs they used them as switches if i remember correctly
some JFETs was broken on it but the problem was i couldn't find any datasheet for them seems like they were in aircrafts for military etc so had to test a bunch of JFETs until it read right on the display lol
Some Power JFETs still available (United Silicon Carbide / Qorvo UJ3N), but expensive and mainly used in specialist areas (motor drives, heating etc).
Thanks for the info
Why you apply positive voltage to Jfet gate?
12:16 - Richard, what is the burden voltage for this meter in the μA range?
Sorry, Don't know. Can I measure that using another multimeter across it in millivolts range or would that in itself affect the reading? Hmmm I guess there is only one way to find out...
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