op amp inputs

for example, LM324

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the data sheet states a differential voltage of as much as 32 volts is permissible. But in the diagram it looks like at about 15 or 20 volts input differential the b/e junctions on one of the inputs would go into reverse conduction. Do I misunderstand or do they use protection circuitry not shown in the diagram.

Reply to
gearhead
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gearhead wrote: > for example, LM324 >

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> the data sheet states a differential voltage of as much as 32 volts is > permissible. > But in the diagram it looks like at about 15 or 20 volts input > differential the b/e junctions on one of the inputs would go into > reverse conduction. > Do I misunderstand or do they use protection circuitry not shown in > the diagram.

Read all the info. You'll see note 1 "Neither of the input voltages must exceed the magnitude of Vcc+ and Vcc-"

Are you referring to the diodes from both inputs to the power supply rails? Those would certainly be the 'limiting' factor.

GG

Reply to
stratus46

I think the PNP input transistors have been doped to produce base emitter reverse break down voltage exceeding the maximum supply voltage rating. This compromise reduces the performance possible with these transistors, but makes using this opamp with open loop inputs, very easy.

Reply to
John Popelish

Jamie wrote: .

...Including all sorts of DC and low frequency (not audio) signal applications, and audio if you can arrange the load to keep only one side of the output totem pole conducting throughout the waveform (or if distortion is not very important, like alarm buzzers or telephone quality voice).

Reply to
John Popelish

And also, if I remember correctly, the LM324 is one of those op-amps that has a discontinued output. meaning, when the follower outputs cross the zero path or near it, there is no minimum bias for both rails being applied to maintain constant current. In a way, this is good in equipment that wants to save on energy when it's used in things like OSC's, voltage comparator etc..

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Reply to
Jamie

You mean 'do the input transistors' b-e junctions go into avalanche breakdown' ?

It's always puzzled me too.

You'd probably need to ask an analog IC designer.

Graham

Reply to
Eeyore

More use of weird and wacky nomenclature from Jamie the Clueless.

Did you mean 'the output stage has zero quiescent current' ? In which case I believe the answer is yes, or 'close to zero'.

I fail to see why you introduced this, since it has nothing to do with the OP's question.

Graham

Reply to
Eeyore

OP's

Yet that is exactly what YOU do.

My answers are normally short and succinct and keep to topic, whereas yours are rambling, off-topic and full of errors including 'using the wrong words'.

Graham

Reply to
Eeyore

Yes, I remember years ago when I run into a problem with a 324 going into oscillation in a particular circuit we were adapting from another op-amp type. the oscillation was only aprox .2 Pk-PK volts. using a feed back cap stopped that how ever, it also added to the miller effect problems. I think what we ended up doing was offsetting the + input via a pot and placing a (-) load on the output to force the OP-amp to correct. We only needed a 0..5 volt output on this OP.

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Reply to
Jamie

OP's

He's been sinking into snarling-mad-dog, insult everybody, Roy L Fuchs mode for some time now. Just another sad insult-bot usenut.

John

Reply to
John Larkin

How big of you !

I learnt a huge amount of electronic knowledge even before I went to Uni/college. Nor did I have anyone to 'put me through' either.

That's because many university lecturers are clueless idiots who are totally divorced from the real world and real world ways of doing things. I had the same problem at UCL.

There is however no excuse not to know what 'quiesent current' means since it's a very widely used term to describe a very important issue. Instead you rambled on about ......

" a discontinued output. meaning, when the follower outputs cross the zero path or near it, there is no minimum bias for both rails being applied to maintain constant current. In a way, this is good in equipment that wants to save on energy when it's used in things like OSC's, voltage comparator etc.. "

Which is a perfect example of the very thing you were criticising. It also makes no damn sense.

Graham

Reply to
Eeyore

Miller effect in an op-amp circuit ?

Once again, you're using technical terms in an inapproriate way.

Graham

Reply to
Eeyore

That makes sense.

Reply to
gearhead

Hit the books trash.

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Reply to
Jamie

OP's

go wipe your ass, you stink. btw, clean your keyboard afterwards. it's most likely full of brown residue and drool.

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Reply to
Jamie

OP's

are

Why are you writing nasty invective to someone who is trying to help? You make it extremely difficult to believe your claims.

--
Al in St. Lou
Reply to
Al in Dallas

OP's

are

Ha, sorry, but you must be new.. stick around for a bit. you'll get the picture. When he's doing any replies to things I write, it's only to help him self.

Maybe you haven't been here long enough.

Have a good day.

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Reply to
Jamie

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