LM324: was (RE: TL082/TLO84?)

[Bissell, Harry]

Gag me. The LM324 has some real problems as an audio op-amp. 
1) the LM324 will not go all the way to ground on a single supply. Usually
only to about 200-300mV above ground (maybe good enough for some apps).
2) the LM324 has non-symetrical current source and sink capability, source
is about 2X higher (source 20-40 mA, sink 10-20mA). This is somewhat
natural, since you have no 'negative' rail to pull down to.
3) If operated on a bipolar supply, the LM324 can exhibit crossover
distortion as it goes from class A to AB (near zero volts). Running a load
resistor to ground will not fix this (though a list member mentioned that
running a load resistor to the negative rail might well do it. I haven't
tried it.)
4) The LM324 may latch to the negative rail if operated on a bipolar supply.
Don't know why, but I've seen it happen

I don't understand the difference of the TL082 vs 84. There are sometimes
problems with amplifiers coupling at the supply pins, and this would be
worse in the quad package. I didn't see any differences in the data sheets
regarding compensation (but max input offset voltage is worse for the 84)

No flames for the LM324, its a good amp but it has to know its place... a
single supply app. with no need to drive too close (or sink too much
current) to ground)   ;-) Harry Bissell
> -----Original Message-----
> From:	Guido Goebertus [SMTP:guidogoe at xs4all.nl]
> Sent:	Monday, March 01, 1999 2:23 PM
> To:	synth-diy at mailhost.bpa.nl
> Subject:	TL082/TLO84?
> 
> Hi Scott,
> 
> You wrote:
> 
> >I see very minor differences between these parts other than 2 amps vs 4
> amps per package.
> >Are there compelling reasons to use one over the other?  I kind of like
> the idea of 4 amps per package.
> 
> There is a small difference.
> I have noticed that a TL 082 works much better as a current to voltage
> converter, especially used by  current controlled amplifiers like the SSM
> 2024 etc. or DAC's.
> If you use a TL 084 in that case you'll get big noise and no useable
> output (after some time).
> I'll guess it has something to do with the built in frequency
> compensation.
> But in most cases a TL084 is a very good choice.
> If speed, low noise and Hi Z inputs are not required the LM 324 is also
> very good choice.
> If my memory serves me well the LM324 's output also really goes to ground
> with a single voltage suply.
> 
> Regards,
> 
> Guido Goebertus