bountyhunter
Well-Known Member
The biggest shock I had was a highly respected and long time analogue designer, complete with pipe and patches on his jacket elbows (sure signs of intellectual gravity and integrity in the UK at the time). I did a design review on his stuff for a particular system. He was trying to sum two analogue voltages by joining them with two resistors and feeding the junction into the non inverting input of a parallel feedback opamp. He also thought it was OK when the flaw was pointed out. Then he didn't know about long tailed pairs either.
Another engineer was asked to design a 10Mhz Xtal oscillator. He kept complaining that he could not get the circuit to work. He had copied a low frequency Xtal oscillator circuit from a 4000 CMOS data book. Also the leads on the Xtal were around 5 inches long.
Another engineer built a switch mode buck PSU with the first capacitor he found laying around the lab. He kept complaining that the data sheet for the chip he was using was a lie, because he could only get 55% efficiency. When I told him that he needed a low ESR capacitor and that the equivalent circuit of a capacitor is quite complex he would not accept it and more or less called me an idiot.
spec
The cap thing is funny. We had a 1 MHz low power switcher chip and we got dozens of calls from people who kept using Tantalum caps with them (despite data sheet warnings to only use ceramic). Amazingly enough, they were functional with the tant caps despite the fact the resonant frequency was an order of magnitude lower than the switch frequency, they just didn't put out much load current.
I had to knock heads with our marketing guys when I published an article explaining some of the facts about capacitors, like how Z5U and Y5F ceramics should be thrown directly in the garbage because they only provide about 20% of rated capacitance...... and make our parts oscillate when they need a minimum capacitance value for stability. I specified X7R on the data sheets for my parts and they didn't like it because they cost a couple of cents more. The funny thing is I have noticed some of my text on ceramic caps quoted verbatim on competitor data sheets.... we all got a really good laugh when competitors copied our errors and typos which happened sometimes.
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