🚀 go-pugleaf

In article <4764@umriscc.isc.umr.edu> dshipley@cs.umr.edu (Dan Shipley) writes:
}Hi, all!
}
}I just got a car audio amplifier from Coustic.  In the manual, it says it  
}uses hex-FET's and NOT to turn the amplifier on if there is no load on the  
}outputs.
}
}I don't know anything about hex-FET's, but it seems unusual that an infinite  
}output impedance would cause damage to a transistor.  However, I'm always  
}learning just how much I don't know, so if someone could enlighten me in the  
}ways of hex-FET's or why this might cause damage, I'd be grateful.

I have to guess:  Since it's a car amplifier, voltage swing is at a
premium.  It therefore probably has a common emitter output stage.  Such
a configuaration has a relatively high unloaded output impedance.  If
the negative feedback loop is of "questionable" stability, the extra
gain, unloaded, could throw the amplifier into instability.  In other
words it might oscillate like crazy at high frequency.  Of course,
without a load, that shouldn't hurt the amplifier.  But it certainly is
embarrassing.  :-)
-- 

Norm Strong  (strong@tc.fluke.com)
2528 31st S.   Seattle WA 98144   USA