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how to supply +15 and -15 v for LM741

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xjackal

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lm741 multisim

hi,
i am trying to build my circuit at home but i couldnt understand how can i supply +and - 15 volt supply for LM741.are there any voltage regulators and should i use adapter?any useful comments would be appreicated.
 

farhada

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minimum supply voltage for lm741cn

You can use 2, one for positive and one for negative, use 7815 for positive and 7915 for negative volate and you are set. Easy and fast.

/Farhad
 

xjackal

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negative power supp with 7815

hi fahrada.thanx for ur help but i knew they exist and i could understand the input voltages.i couldnt see it from the datasheet.and whats the difference between using this regualtors and inversing the positive terminal.i mean i cant understand why cant we use +15v inversely as -15?
 

v_c

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power supply lm741 as series regulators

You can take two 15V supplies and connect them in series and make the midpoint of the power supplies your reference. Then the top voltage with respect reference will be +15V and the bottom voltage with respect to supply will be -15V.

--------------> +15V (with respect to reference)
+
15V
-
--------------> reference
+
15V
-
--------------> -15V (with respect to reference)

This is quite easy to do if you have a lab power supply with dual outputs.

Best regards
v_c
 

IanP

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15v positive negative ground

Other option is so called "virtual ground" ..
The principle of virual ground is shown below ..
Basically what you need is a single 30V power supply and divide this voltage into two equal halves making the center point your new ground reference ..
More examples and explenations can be found here:
https://tangentsoft.net/elec/vgrounds.html

Regards,
IanP

BTW: 741 will happily work of anything between +/-4.5V (9V) to +/-15V (30V), so if your application doesn't require output voltage of +/-12V, or more, you may consider lowering supply voltage from +/-15 to whatever you have available ..
 

    xjackal

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ptmsl

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how to lm741

i cant understand why cant we use +15v inversely as -15?
7815 and 7915 are both "series" regulators meaning that they are placed in series with the supply rail that they regulate. +15V or -15V is just a matter of which rail you choose as "ground" that is your reference. So if you use 7815 as a negetive regulator you would regulate your "ground" connection. That may work for single supply but if you need both positive and negative supplies the negative rail of the +15V supply would connect to the positive supply of the -15V and then the return current (ground) of the positive supply would pass through the 7815 of the negative supply.
 

nutty boy

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dividing +/- 15 volts from +15v power supply

I think u can get the required voltages by using single transformer with center tab
 

elantra

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lm741 supply voltage

Answers above is very clear. You should remember that every voltage is relative, you can choose any voltage as zero. for example you can splite a 5v supply as 2.5V and -2.5V.
 

xjackal

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voltage supply for lm741

yeah.thanks but i got it before with the first posts.thank u.idont need any more info.
 

kohtwe

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lm741 volt

hi,

you can see supply +15 and - 15 volt supply voltage regulators for LM741. This attach file, drawning the Electronic Workbeanch Multisim 8.


You can use two phases, one for positive and one for negative, use 7815 for positive and 7915 for negative volage.

I don't attachment.
 

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