I think I've entered the twilight zone.Okay, one more time.... I did not design the circuit to be turned on and left that way.So, since every single person who looks at this is assuming that they will be forced against there better judgement to use it incorrectly, I will update the design and test it to make sure it is idiot proof.
Oops, you're right the minimum hfe is around 40. But average current isn't the point, this is about idiot-proof non-self-destructive design. If the average is 200mA then the max is 400mA which will melt things if it gets stuck on.
I don't see any need for a class A amp, common emitter class B should be plenty good enough and use less power. Sound quality certainly isn't the issue. An emitter follower would be good enough I think.
This article goes into depth of the single gate amplifier. Scroll down to page 8.http://www.ece.ucsb.edu/Faculty/rodwell/Classes/ece2c/labs/Lab_2_2C_2007.pdfWe don't need it biased to operate in the linear region since the tone output is either on or off - hence the amplifiers output can be on or off as well.
... I will update the design and test it to make sure it is idiot proof.
Quote... I will update the design and test it to make sure it is idiot proof.From a practical viewpoint, this should be Rule #1, since everybody who's ever done anything at all knows how large the idiot population really is.
Quote from: oric_dan on Apr 03, 2013, 09:32 pmQuote... I will update the design and test it to make sure it is idiot proof.From a practical viewpoint, this should be Rule #1, since everybody who's ever done anything at all knows how large the idiot population really is."Make it idiot proof and someone will make a better idiot."
For years, all of my pcbs have used simple series-R protection on the I/O pins, andno one ever blew up one of my boards [at least that owned up to it]. OTOH, back in the days of yore, another guy was selling similar boards with no protection and all smt parts, and every single day on the associated forum, some poor guy cameon crying he had blown his xxxx board. Some designs are "more" idiot-proof thanothers, I guess.
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