ECE3400 L42: Introduction to JFETs (Analog Electronics, Georgia Tech course)

[@hpoz222]

I would absolutely love a series on pro audio circuitry! I also have a special place in my heart for JFETs, particularly because the 1176 is my favorite compressor

[@jeffdeez1]

Another vote for this, yes please.. compressors, equalisers.. all of it. 🙏🏼

[@paulnation2315]

I would love to see the special topics class for audio hardware. The synth class playlist is one of the best series of educational videos and inspired me to prototype my own modular synth. You are the GOAT!

[@georgegkountouras4311]

11:40 Very interested in a pro audio circuits class! 🤩

[@johnwilliamson467]

Having been around this subject for 50 plus years I find your tone and style of teaching to to be rather relaxing in a fine way. Mr Roger would have found to be a fine instructor ( no sarcasm on my part. ). I wish you had been my instructor for many of the class I have taken . Also a good understanding of the subject . Bravo. Saturation region could be called the pentode using the tube (valve) term giving clarity to the bjt saturation term problem .

[@EuphoricDan]

FYI for SPICE modeling Mike Engelhardt recently said he figured out and added an accurate way to simulate JFETs in QSpice. According to him (and he showed graphs for whatever that's worth) no other SPICE can accurately model them. I just figured it's worth mentioning here that (at least for now) all other SPICE simulations pretty heavily distort JFETs.

[@wbeaty]

I commonly encounter JFETs in two places, both inside professional research instruments: discrete matched-pairs in extreme low noise front ends (neural axon preamps, "Patch-clamp," and also in cryo-cooled front-ends used for Ortec's HPGe germanium scintillation detectors.) If you want a low-noise preamp, JFET plus liquid nitrogen FTW. Once I dissected a dead Axopatch 200B probe. Inside I found a -40C peltier-cooled block, and on it a lead bonded chip-die for matched pair of JFETS. Little wonder that the thing costs $20K, and also is capable of monitoring picoamps activity of a single ion-channel in the cell membrane of a neuron.

[@Lantertronics]

Wow, I had no ideal Peltier cooling could be used to get that cold!

[@wbeaty]

@@Lantertronics Oops, wrong. I looked it up and found that, during malfunction, it went down to -20C. Normally it's supposed to be set to -15C by feedback. A chilled block protrudes into the tiny chamber, only about 0.5 square cm. It contains a hunk of dessicant, to prevent frost! Photos of the tiny hybrid module in the probe guts, CV-203BU headstage repair. For the liquid nitrogen cooler, the PCB is contained in hard vacuum. For that detector they used single SK152-2 or SK147 jfets, for low noise with low input capacitance.

[@uanpis4457]

i would absolutely love to watch a class on pro audio recording circuits!!!

[@christopherventer6391]

I would be 100% in for a pro audio series. there are a lot of very interesting circuits out there particularly for compression, dynamics, and EQ.

[@gwalla]

I would love to see you tackle the analysis of the "Harness" unit invented by the great guitarist Allan Holdsworth. There's a series here on YT of a guy reverse engineering it, but he's definitely winging it. A pretty odd little gadget (not even sure it's appropriate to call it an "effect").

[@Lantertronics]

Ah, I hadn't heard of it. It looks really interesting!

[@aly.3921]

love your videos.. yes please do more explanations on studio equipment processors thank you

[@davegeorge7094]

I dig the virtual resistor thing here!

[@brendanbarbour8568]

Hi Aaron, I've only just discovered your KZbin channel and will for sure be working through the episodes on valve amps. I would be very interested in a "Special Topic" series on high performance input stages, Mic Amps Mixers and EQ's should you take the time to put such together. I've been fortunate to have come across a good number of such stages that have found application in professional recording studios over the years. It would be interesting to discover whether and active input stage could approach the performance of a transformer balanced mic input in terms of EIN and THD with the necessary Dynamic Range.

[@LogoRR]

would certainly be interested in the pro audio circuitry series!

[@milos_radovanovic]

Love the video! How about one on a UJT?

[@edsavage6214]

I'd love a pro audio circuit analysis series!

[@zvukofor]

I can confirm: drain and source are interchangeable in j308...310 series FETs, at least for audio. +1 on pro audio circuits series, please! And - thank you so much for your lectures!

[@johnwilliamson467]

yes on the pro audio topic ,

[@BoxingDayAC]

11:40 Microphone preamps! The input, gain and output stages would be nice to see analyzed. I'm curious why low kHz input impedance is industry standard.

[@davebing11]

Low input impedance = low thermal noise which can be dominant in low noise audio circuits

[@profdc9501]

One particular relevant application of JFETs nowadays is power devices. Silicon carbide devices often come as JFETs, and because of symmetry JFETs may be used as switches for actively commutated mixers. JFETs also have low capacitance, high input impedance, and low noise figure for RF probes. You can use a differential pair of them with an op-amp to get a low noise figure amplifier.

[@Lantertronics]

I am very happy to see they are not forgotten and still find applications!

[@Aleph_Null_Audio]

I'd be very interested in lectures about JFETs in musical circuits!

[@fixfaxerify]

There is interest in such a thing

[@GianmarioScotti]

At 7:34, when you say "and we're assuming that we're in saturation", you underline Vgs less or equal to Vp, but that is not the condition for saturation.

[@FreshPanoRamaMaker]

This explanations are excellent 👌. @13:30 is a point that confused me alot in the past. I used a JFET as AGC (automatic gain control) for a circuit, so the FET works in the ohm/triod region as a variable resistor? I have to watch this video again 😂.

[@komisar81]

Pro audio circuitry, I'm in. A definite double plus good. Excuse the Orwellian speak.

[@kylew706]

Very interested in pro audio class!

[@thewhitefalcon8539]

The JFE150 schematic diagram shows symmetrical drain and source although it may still be asymmetrical for other reasons. CL and CH aren't symmetricalm

[@lambdaprog]

A JFET mixer is a good utilization of symmetry.

[@third_ear]

11:59 I'm interested in such a thing!

[@millejosh5028]

Hello, not sure if you’ll read this, but I came across your video on the prophet VCO card and I was wondering if you have any recommendations for building a test pcb for SSM 2030 and SSM 2040 ICs? I have a bunch I need to test but no prophet 5

[@comPOed]

One more comment in support of audio related JFETs

[@kierenmoore3236]

So, why are MOSFETs in favour/considered more sexy, then … ?

[@thewhitefalcon8539]

Much higher maximum gate voltage relative to pinch-off, I think? A JFET can only make the conductance worse than a default silicon level but a MOSFET can make it better?

[@wellscampbell9858]

Is it Dre? Is it Dre? That's what they say. Every single M______F______in day.

[@Hellcommander245]

1.) Dre 2.) JFET 3.) The Alamo!!!