AoE x-Chapters, High-Speed op-amps section, DRAFT

I met one guy who worked for Lockheed (I think) who did big TTL logic boards with no bypass caps. All his stuff worked.

An FPGA does deserve enough bulk C so the supply doesn't droop much when clocks start or stop or something, amps of Vcc-core step maybe.

I don't think I've ever made a board that had too few bypass caps. How many million caps have I wasted?

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nd an error in the production meant none was mounted

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imagine fixing it, here's a reel of caps and soldering iron, see you in a w eek

Earl Muntz is said to have walked around the R&D lab with a pair of wire cutters in his pocket. Snip .. out went a cap. "See? Nothing happened! You are wasting money". Other times .. snip .. phseeeooouu .. PHUT ... "Well, you better put that one back in".

The Muntz TVs only worked close to TV stations. They didn't have much gain. Not enough tubes in the IF strip.

He snipped screen bypass caps, which didn't help the gain situation either.

Even on radio chips I used to put them, because off-chip capacitors are not much use above 1GHz in a package with bondwires. Also, I had to put some resistors of various values in series with some fraction of the on-chip decoupling capacitors, because otherwise there would be ringing on the on-chip supply voltage due to resonance with the bondwire inductance.

Depends. I had an early Goldstar (now LG) microwave that gained time when used; found that they had a board of TTL for the clock, with no bypass capacitors at all. Two little 0.01 uF ceramics, and it kept correct time for a decade.

The assumption, of course, is that every TV manufactured would be identical to this one. ...and stay that way for its lifetime.

Not for life, only until its warranty is up 8-)

There would have been a much cheaper solution. They could have declared this a feature and sold it as having a time machine function. "Our microwave catapults you into the future!".

Well, I did say *its* lifetime.

Shoddy products usually still have a lot of life left in them but the performance becomes so bad and the potential repairs so expensive that people give them up prematurely. Cars of certain brands are a classic example.

Often a sign of shoddy engineering. We're taught that designs should not ask for more out of a part than can be delivered at end of life. For example, BJT beta. Good designs should perform acceptably with low betas.

On a sunny day (19 Jul 2019 17:03:28 -0700) it happened Winfield Hill wrote in :

That is a bit over over-simplification.

In the tube days you would design keeping in mind 100% or so degeneration of the thing.

Semiconductors OTOH do not really degrade that much (unless some .. uses the be zener with kA ;-0 ). so no problem relying in some circuits of a high beta. Simple BC547 etc have an A, B, C suffix and a minimum beta specified for each.

If you are against using that, then why all the stories about the evolution of MOSFETs?

In MY opinion (open fire if you feel the need) if I need some part I use google for the specs I want. I could not care less what's in those things as long as it meets those specs. Same with processors and more complicated chips.

The story about IR is interesting though, deceasing capacitances over time too. I use IRLZ34N a lot. for low voltage stuff.

It can have many causes. In the case of a car company I have inside info that a main factor was quality control and here mainly incoming inspection. Or to a large extent a lack thereof.

Not so much for the large tube in the HV and horizontal deflection section. On color TVs those had to be replaced quite regularly. In Europe that was the PL509 and later PL519.

They do if treated harshly.

Quote page 5 "If the transient temperature resulting from an avalanche event, as illustrated in Figure 6, rises beyond a recommended rated value, the device risks being degraded".

Like the exorbitant wattage rating of some FETs? Good luck.

Sounds like some voice audio at :56 and 1:05.

Mikek

A related concern is the longevity of LEDs for lighting; while selected LEDs have high efficiency (140 lm/w), the run-of-the-mill is more like 90 lm/w and will degrade with time. The better manufacturers that give lamp specs (Philips) are promising 75 lm/w and years of service life.

In the old days (probably for chemistry reasons) the LED recommendation was to expect 30% per year degradation; I've seen optointerrupters become inoperable with just a few months of use, that were assembled in circuits with factory-adjusted trimmers. That wasn't good engineering, IMHO.

Yes, I bought into this line of thinking. I purchased about six of the more-expensive, higher-quality Philips LED bulbs. Four of the six have failed, many after only a few hundred hours, and none anywhere near their claimed lifetime. They were installed in dropped-down-from-the-ceiling fixtures, with lots of room and generous airflow. No autopsies were performed.

Does anyone what know the common failure modes are?