kids these days

Sep 26, 2024 Last reply: 1 year ago 75 Replies
J

Both true. I would have gotten the bit about emitter followers being able to oscillate, because while they have no voltage gain, they do have power gain, so can be made to oscillate nicely with a multi-tapped ferrite pot core inductor and a film capacitor. This is how the old Touch-Tone keypads worked, with Germanium transistors even. Later were silicon.

My equivalent to your emitter follower test is higher-level, because I was in the software labs in those days, but we were interfacing to hardware.

I would give the candidate a 11x17 inch sheet of paper and a pencil, and ask the candidate to draw a diagram of the components of their senior project, and walk me through it step by step. This was quite effective at eliminating the poseurs, as they could not get much beyond high-level platitudes. People who had actually designed a built something would not run out of deep details.

And I was on the receiving end of such a question when I was job seeking in the 1970s or so. There was this startup which was building something that ran on SEL 32/55 midi computers, an IBM 360 clone optimized for process control. (SEL 32/55s are now a chip.)

The question was to diagram and explain how an I/O Channel Control worked. It's a linked chain of data blocks, each block specifying an action or setting. In those days, these blocks were data structured usually generated with macros, but in earlier days one just wrote the data structure directly in hex.

Anyway I passed, but the company was a bit too anarchic for my taste. Many years later, my main interviewer applied for a job (not knowing that I was the manager), and I hired him. The very fact that he could follow what I was saying back in the day was enough proof of capability. Small world.

Joe Gwinn

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E

...

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503 (pdf page 37)

One thing I just noticed is that 2N4302 is n channel but shown as p channel.

Anyone know of a part I can still buy which is sufficiently equivalent?

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C

Congratuations, Phil. You're hired! :-)

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J

You could bootstrap a collector resistor and get about the same effect.

The Supertex depletion fets make nice constant-current loads too. They are very repeatible, unlike jfets.

What's the expected current in the jfet?

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E

"john larkin" snipped-for-privacy@glen--canyon.com wrote in message news: snipped-for-privacy@4ax.com...

The current in the FET is about 50 uA in this version which has been adusted for 12V rather than 24V power.

Looks like J113 is a reasonable replacement in this circuit, and it is available.

Version 4 SHEET 1 1144 1280 WIRE -272 -144 -400 -144 WIRE 112 -144 -272 -144 WIRE 352 -144 112 -144 WIRE 544 -144 352 -144 WIRE -272 -96 -272 -144 WIRE 112 -96 112 -144 WIRE 352 -96 352 -144 WIRE 544 -16 544 -144 WIRE -272 16 -272 -32 WIRE 112 16 112 -16 WIRE 192 16 112 16 WIRE 352 32 352 -16 WIRE 480 32 352 32 WIRE 112 64 112 16 WIRE 192 112 192 80 WIRE 64 128 16 128 WIRE 112 176 112 160 WIRE 176 176 112 176 WIRE 112 192 112 176 WIRE 272 208 240 208 WIRE 544 208 544 80 WIRE 544 208 336 208 WIRE -400 256 -400 -144 WIRE 352 272 352 32 WIRE 16 304 16 128 WIRE 112 304 112 272 WIRE 112 304 16 304 WIRE 112 320 112 304 WIRE 240 320 240 208 WIRE 240 320 112 320 WIRE 288 320 240 320 WIRE 112 352 112 320 WIRE -288 400 -576 400 WIRE -240 400 -288 400 WIRE -224 400 -240 400 WIRE -128 400 -160 400 WIRE -16 400 -48 400 WIRE 48 400 -16 400 WIRE 352 400 352 368 WIRE 432 400 352 400 WIRE 352 416 352 400 WIRE 544 480 544 208 WIRE 592 480 544 480 WIRE 688 480 656 480 WIRE 832 480 768 480 WIRE 880 480 832 480 WIRE -16 496 -16 400 WIRE 16 496 -16 496 WIRE 112 496 112 448 WIRE 112 496 80 496 WIRE 112 512 112 496 WIRE 224 512 112 512 WIRE -240 528 -240 400 WIRE -16 528 -16 496 WIRE 352 528 352 496 WIRE 432 528 352 528 WIRE 112 544 112 512 WIRE 352 544 352 528 WIRE -576 608 -576 400 WIRE 832 608 832 480 WIRE -16 656 -16 608 WIRE 352 656 352 624 WIRE 352 656 -16 656 WIRE 544 672 544 480 WIRE 688 672 544 672 WIRE 112 688 112 624 WIRE 112 688 -16 688 WIRE -16 720 -16 688 WIRE 112 720 112 688 WIRE 352 720 352 656 WIRE 432 720 432 528 WIRE 544 720 544 672 WIRE 688 720 688 672 WIRE -576 832 -576 688 WIRE -400 832 -400 336 WIRE -400 832 -576 832 WIRE -240 832 -240 608 WIRE -240 832 -400 832 WIRE -16 832 -16 784 WIRE -16 832 -240 832 WIRE 112 832 112 800 WIRE 112 832 -16 832 WIRE 352 832 352 800 WIRE 352 832 112 832 WIRE 432 832 432 784 WIRE 432 832 352 832 WIRE 544 832 544 800 WIRE 544 832 432 832 WIRE 832 832 832 688 WIRE 832 832 544 832 WIRE -576 880 -576 832 WIRE 224 896 224 512 WIRE 256 896 224 896 WIRE 496 896 336 896 WIRE 544 896 496 896 WIRE 688 896 688 784 WIRE 688 896 624 896 WIRE 224 1024 224 896 WIRE 256 1024 224 1024 WIRE 368 1024 336 1024 WIRE 400 1024 368 1024 WIRE 496 1024 496 896 WIRE 496 1024 464 1024 WIRE 224 1136 224 1024 WIRE 256 1136 224 1136 WIRE 368 1136 368 1024 WIRE 368 1136 320 1136 FLAG -576 880 0 FLAG 192 112 0 FLAG -288 400 input FLAG -272 16 0 FLAG 832 480 output DATAFLAG 496 208 "round(($)*100)/100" DATAFLAG 400 528 "round(($)*100)/100" DATAFLAG 304 656 "round(($)*100)/100" DATAFLAG 16 400 "round(($)*100)/100" DATAFLAG 160 512 "round(($)*100)/100" DATAFLAG 64 688 "round(($)*100)/100" DATAFLAG 160 16 "round(($)*100)/100" DATAFLAG 176 320 "round(($)*100)/100" DATAFLAG 400 400 "round(($)*100)/100" DATAFLAG 400 32 "round(($)*100)/100" DATAFLAG 160 176 "round(($)*100)/100" DATAFLAG -352 -144 "round(($)*100)/100" SYMBOL res 96 -112 R0 SYMATTR InstName R1 SYMATTR Value 47k SYMBOL voltage -400 240 R0 WINDOW 123 0 0 Left 0 WINDOW 39 -151 71 Left 2 WINDOW 3 -79 36 Left 2 SYMATTR SpiceLine Rser=0.1 SYMATTR Value 12 SYMATTR InstName V1 SYMBOL npn 48 352 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res 96 176 R0 SYMATTR InstName R2 SYMATTR Value 27k SYMBOL npn 480 -16 R0 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL res 336 -112 R0 SYMATTR InstName R3 SYMATTR Value 22k SYMBOL npn 288 272 R0 SYMATTR InstName Q3 SYMATTR Value 2N3904 SYMBOL polcap 176 16 R0 SYMATTR InstName C2 SYMATTR Value 68µ SYMBOL res 96 528 R0 SYMATTR InstName R4 SYMATTR Value 470 SYMBOL res 96 704 R0 SYMATTR InstName R5 SYMATTR Value 39k SYMBOL res -32 512 R0 WINDOW 0 -41 40 Left 2 WINDOW 3 -63 76 Left 2 SYMATTR InstName R6 SYMATTR Value 270k SYMBOL cap 80 480 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 470p SYMBOL polcap -32 720 R0 SYMATTR InstName C3 SYMATTR Value 22µ SYMBOL res -32 384 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 1k SYMBOL polcap -160 384 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 1µ SYMBOL res -256 512 R0 WINDOW 0 40 38 Left 2 WINDOW 3 36 74 Left 2 SYMATTR InstName R8 SYMATTR Value 68k SYMBOL res 528 704 R0 SYMATTR InstName R9 SYMATTR Value 3.3k SYMBOL cap 336 192 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C5 SYMATTR Value 10p SYMBOL res 336 528 R0 WINDOW 0 -52 35 Left 2 WINDOW 3 -58 72 Left 2 SYMATTR InstName R10 SYMATTR Value 5.6k SYMBOL res 336 704 R0 WINDOW 0 -53 28 Left 2 WINDOW 3 -47 61 Left 2 SYMATTR InstName R11 SYMATTR Value 10k SYMBOL res 336 400 R0 WINDOW 0 -59 36 Left 2 WINDOW 3 -61 76 Left 2 SYMATTR InstName R12 SYMATTR Value 2.2k SYMBOL res 352 880 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R13 SYMATTR Value 680k SYMBOL res 640 880 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R14 SYMATTR Value 1.5k SYMBOL res 352 1008 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R15 SYMATTR Value 24k SYMBOL cap 320 1120 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 3.3n SYMBOL cap 464 1008 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C7 SYMATTR Value 10n SYMBOL polcap 672 720 R0 SYMATTR InstName C8 SYMATTR Value 1µ SYMBOL polcap 416 720 R0 SYMATTR InstName C9 SYMATTR Value 100µ SYMBOL polcap -288 -96 R0 SYMATTR InstName C10 SYMATTR Value 220µ SYMBOL polcap 592 496 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName C11 SYMATTR Value 1µ SYMBOL res 784 464 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R16 SYMATTR Value 100 SYMBOL res 816 592 R0 SYMATTR InstName R17 SYMATTR Value 1000k SYMBOL voltage -576 592 R0 WINDOW 3 -283 51 Left 2 WINDOW 123 -283 79 Left 2 WINDOW 39 -283 107 Left 2 SYMATTR Value SINE(0 0.1 1000) SYMATTR Value2 AC 0.1 0 SYMATTR SpiceLine Rser=0 SYMATTR InstName V2 SYMBOL njf 64 64 R0 WINDOW 0 -8 -8 Left 2 WINDOW 3 -51 22 Left 2 SYMATTR InstName J1 SYMATTR Value J113 TEXT -864 808 Left 2 !.ac oct 20 5 3000000 TEXT -864 880 Left 2 ;.tran 100m

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E

"john larkin" snipped-for-privacy@glen--canyon.com wrote in message news: snipped-for-privacy@4ax.com...

It can't be denied that a bootstrap version has similar, maybe near enough identical performance and eliminates the FET completely.

Version 4 SHEET 1 1144 1280 WIRE -272 -144 -400 -144 WIRE 112 -144 -272 -144 WIRE 352 -144 112 -144 WIRE 544 -144 352 -144 WIRE -272 -96 -272 -144 WIRE 112 -96 112 -144 WIRE 352 -96 352 -144 WIRE 544 -16 544 -144 WIRE -272 16 -272 -32 WIRE 112 32 112 -16 WIRE 208 32 112 32 WIRE 352 32 352 -16 WIRE 480 32 352 32 WIRE 208 80 208 32 WIRE 112 128 112 32 WIRE 272 208 240 208 WIRE 544 208 544 80 WIRE 544 208 336 208 WIRE -400 256 -400 -144 WIRE 352 272 352 32 WIRE 112 320 112 208 WIRE 240 320 240 208 WIRE 240 320 112 320 WIRE 288 320 240 320 WIRE 112 352 112 320 WIRE 352 384 352 368 WIRE 432 384 352 384 WIRE -288 400 -576 400 WIRE -240 400 -288 400 WIRE -224 400 -240 400 WIRE -128 400 -160 400 WIRE -16 400 -48 400 WIRE 48 400 -16 400 WIRE 208 400 208 144 WIRE 352 400 352 384 WIRE 352 400 208 400 WIRE 352 416 352 400 WIRE 544 480 544 208 WIRE 592 480 544 480 WIRE 688 480 656 480 WIRE 832 480 768 480 WIRE 880 480 832 480 WIRE -16 496 -16 400 WIRE 16 496 -16 496 WIRE 112 496 112 448 WIRE 112 496 80 496 WIRE 112 512 112 496 WIRE 224 512 112 512 WIRE -240 528 -240 400 WIRE -16 528 -16 496 WIRE 352 528 352 496 WIRE 432 528 352 528 WIRE 112 544 112 512 WIRE 352 544 352 528 WIRE -576 608 -576 400 WIRE 832 608 832 480 WIRE -16 656 -16 608 WIRE 352 656 352 624 WIRE 352 656 -16 656 WIRE 544 672 544 480 WIRE 688 672 544 672 WIRE 112 688 112 624 WIRE 112 688 -16 688 WIRE -16 720 -16 688 WIRE 112 720 112 688 WIRE 352 720 352 656 WIRE 432 720 432 528 WIRE 544 720 544 672 WIRE 688 720 688 672 WIRE -576 832 -576 688 WIRE -400 832 -400 336 WIRE -400 832 -576 832 WIRE -240 832 -240 608 WIRE -240 832 -400 832 WIRE -16 832 -16 784 WIRE -16 832 -240 832 WIRE 112 832 112 800 WIRE 112 832 -16 832 WIRE 352 832 352 800 WIRE 352 832 112 832 WIRE 432 832 432 784 WIRE 432 832 352 832 WIRE 544 832 544 800 WIRE 544 832 432 832 WIRE 832 832 832 688 WIRE 832 832 544 832 WIRE -576 880 -576 832 WIRE 224 896 224 512 WIRE 256 896 224 896 WIRE 496 896 336 896 WIRE 544 896 496 896 WIRE 688 896 688 784 WIRE 688 896 624 896 WIRE 224 1024 224 896 WIRE 256 1024 224 1024 WIRE 368 1024 336 1024 WIRE 400 1024 368 1024 WIRE 496 1024 496 896 WIRE 496 1024 464 1024 WIRE 224 1136 224 1024 WIRE 256 1136 224 1136 WIRE 368 1136 368 1024 WIRE 368 1136 320 1136 FLAG -576 880 0 FLAG -288 400 input FLAG -272 16 0 FLAG 832 480 output DATAFLAG 496 208 "round(($)*100)/100" DATAFLAG 400 528 "round(($)*100)/100" DATAFLAG 304 656 "round(($)*100)/100" DATAFLAG 16 400 "round(($)*100)/100" DATAFLAG 160 512 "round(($)*100)/100" DATAFLAG 64 688 "round(($)*100)/100" DATAFLAG 160 32 "round(($)*100)/100" DATAFLAG 160 320 "round(($)*100)/100" DATAFLAG 400 384 "round(($)*100)/100" DATAFLAG 400 32 "round(($)*100)/100" DATAFLAG -352 -144 "round(($)*100)/100" SYMBOL res 96 -112 R0 SYMATTR InstName R1 SYMATTR Value 47k SYMBOL voltage -400 240 R0 WINDOW 123 0 0 Left 0 WINDOW 39 -151 71 Left 2 WINDOW 3 -79 36 Left 2 SYMATTR SpiceLine Rser=0.1 SYMATTR Value 12 SYMATTR InstName V1 SYMBOL npn 48 352 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res 96 112 R0 SYMATTR InstName R2 SYMATTR Value 150k SYMBOL npn 480 -16 R0 SYMATTR InstName Q2 SYMATTR Value 2N3904 SYMBOL res 336 -112 R0 SYMATTR InstName R3 SYMATTR Value 22k SYMBOL npn 288 272 R0 SYMATTR InstName Q3 SYMATTR Value 2N3904 SYMBOL polcap 192 80 R0 SYMATTR InstName C2 SYMATTR Value 10µ SYMBOL res 96 528 R0 SYMATTR InstName R4 SYMATTR Value 470 SYMBOL res 96 704 R0 SYMATTR InstName R5 SYMATTR Value 39k SYMBOL res -32 512 R0 WINDOW 0 -41 40 Left 2 WINDOW 3 -63 76 Left 2 SYMATTR InstName R6 SYMATTR Value 270k SYMBOL cap 80 480 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C1 SYMATTR Value 470p SYMBOL polcap -32 720 R0 SYMATTR InstName C3 SYMATTR Value 22µ SYMBOL res -32 384 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 1k SYMBOL polcap -160 384 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C4 SYMATTR Value 1µ SYMBOL res -256 512 R0 WINDOW 0 40 38 Left 2 WINDOW 3 36 74 Left 2 SYMATTR InstName R8 SYMATTR Value 68k SYMBOL res 528 704 R0 SYMATTR InstName R9 SYMATTR Value 3.3k SYMBOL cap 336 192 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C5 SYMATTR Value 10p SYMBOL res 336 528 R0 WINDOW 0 -52 35 Left 2 WINDOW 3 -58 72 Left 2 SYMATTR InstName R10 SYMATTR Value 5.6k SYMBOL res 336 704 R0 WINDOW 0 -53 28 Left 2 WINDOW 3 -47 61 Left 2 SYMATTR InstName R11 SYMATTR Value 10k SYMBOL res 336 400 R0 WINDOW 0 -59 36 Left 2 WINDOW 3 -61 76 Left 2 SYMATTR InstName R12 SYMATTR Value 2.2k SYMBOL res 352 880 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R13 SYMATTR Value 680k SYMBOL res 640 880 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R14 SYMATTR Value 1.5k SYMBOL res 352 1008 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R15 SYMATTR Value 24k SYMBOL cap 320 1120 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C6 SYMATTR Value 3.3n SYMBOL cap 464 1008 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName C7 SYMATTR Value 10n SYMBOL polcap 672 720 R0 SYMATTR InstName C8 SYMATTR Value 1µ SYMBOL polcap 416 720 R0 SYMATTR InstName C9 SYMATTR Value 100µ SYMBOL polcap -288 -96 R0 SYMATTR InstName C10 SYMATTR Value 220µ SYMBOL polcap 592 496 R270 WINDOW 0 32 32 VTop 2 WINDOW 3 0 32 VBottom 2 SYMATTR InstName C11 SYMATTR Value 1µ SYMBOL res 784 464 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R16 SYMATTR Value 100 SYMBOL res 816 592 R0 SYMATTR InstName R17 SYMATTR Value 1000k SYMBOL voltage -576 592 R0 WINDOW 3 -283 51 Left 2 WINDOW 123 -283 79 Left 2 WINDOW 39 -283 107 Left 2 SYMATTR Value SINE(0 0.1 1000) SYMATTR Value2 AC 0.1 0 SYMATTR SpiceLine Rser=0 SYMATTR InstName V2 TEXT -864 808 Left 2 !.ac oct 20 5 3000000 TEXT -864 880 Left 2 ;.tran 100m

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B

John Larkin doesn't seem to understand the two transistor emitter-coupled monostable.

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C

Doesn't mean much as specified. Voltage with respect to what?

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J

Yes.

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We have a direct account with Lundt.

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J

The planet that we all share. It should be obvious in the sketch that I draw.

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C

On 30/09/2024 19:11, john larkin wrote: <snip>

Along with a colleague, I interviewed someone for a repair technician's job a few years back. Among the questions was a simple common emitter single transistor stage which we asked him to explain.

He blew us away. He knew *far* more detail than either of us. Turned out he was a s*it-hot analog designer looking for a less stressful job as he wound down to retirement. He turned out to be brilliant at his new job, and mentored a lot of younger people. He left when the company was bought by a large US corporation with the concomitant mind-numbing treacle-wading bullshit. [Me too!]

[Among the other questions were to make an Xor using two-input Nands, show a methodology for calculating a square root where that function isn't available, and tell us at what temperature solder melts.]
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C

You were lucky, then. Designers typically don't make good repair technicians and vice-versa. The two types think in fundamentally different ways.

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J

It makes no sense that europeans are a zillion miles from the places that grow chocolate, but make such good stuff. The Ritter Sport dark stuff is great.

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P

Nah, it’s all from the sun-drenched tropical mountains of Holland.

Cheers

Phil Hobbs

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A

Most of it comes from (is processed by) Cacao de Zaan, a factory in the west of the Netherlands, below sea level. A very long time ago I supervised the design and commissioning of a laboratory data collection and automation system for them. After working there for a week I could not eat chocolate for some weeks, the intense smell was too much.

Arie

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J

There's actually a ski resort in the Netherlands.

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J

Yep, with mountain summits culminating at 40 cm above the local water level. The smell of cocoa permeates the whole area. I had an uncle working at Verkade.

Jeroen Belleman

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P

My grandfather spent a few years being closely concerned with small differences of elevation in Flanders.

Cheers

Phil Hobbs

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J

I see the trend, good circuit designers retiring and not being replaced.

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J

Where I grew up, 318 Broadway Street in New Orleans, we looked UP at ships on the Mississippi river.

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