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Old 15th December 2003, 06:04 AM   #1
cm961 is offline cm961  Canada
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Exclamation National's mistake (AN-1192)?

Hey guys,

I was reading National's AN-1192 again (like anyone here hasn't read it). Anyway, I'm confused about the voltage regulators for the input stage op-amp. They're using LM78L15s and LM79L15s which have a maximum input voltage of 23V. But the supply voltage is 42V. Soo..... wouldn't the regulators blow up?

If I'm right, then what do people use to lower the main supply to an acceptable level for op-amps (NE5532s in my case)? My rail supplies are +- 28V.

Pete
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Old 15th December 2003, 07:50 AM   #2
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Default lm78l15acz



i think the said regulator has a max. input of 35v and a min. of 16v with a current output of 100ma.

i have seen the literature of the 1192 but have not really scrutyinize the schem. the only thing that interested me was the interconnection of the bridge/parallel circuit. IC audio power amps is not my cup of tea.
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Old 15th December 2003, 08:27 AM   #3
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Default lm78l15acz

hi,

now i've seen the an1192 literature again. according to specs. if you want to drive a 4 ohm load you power it with +/-28v. if for 8ohms load you power that with +/-35v. now this voltages are all within the specs of the 78L15
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Old 15th December 2003, 08:28 AM   #4
UrSv is offline UrSv  Sweden
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The maximum input is depending on manufacturer but AFAIK none has a maximum of 23 V input. The National version of LM7815 has a maximum input of 35 V. The 23 V specified in the datasheet is the figure used when measuring the specs listed if I'm not making a mistake.
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Old 15th December 2003, 08:36 AM   #5
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cm961, allways look at "absolute maximum ratings" in the datasheet. Have you done that?

35 volts is the normal value.
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Old 15th December 2003, 04:03 PM   #6
cm961 is offline cm961  Canada
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Thanks for clearing that up guys, I was very very confused. I guess I shouldn't design circuits at 2:30am...

Thanks again,
Pete
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