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Problem with Vcc and Vss for LM741 op-amp

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syee10

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Hi all,

I have an opamp LM741 which require a Vcc and Vss to operate. I plan to give it +15V Vcc and -15V Vss. The problem is when i only connect +15V to the Vcc pin (pin7) on the opamp, the Vss pin (pin4) shows +13V plus plus when i measure it with voltmeter. I wonder why this happen? Is this normal? The Vss pin should shows 0V because i not yet connect a -15V to pin4,right?
 

Re: Op-Amp LM741 problem

Not really necessary.(until you connect the pin to Ground)
If you have a look at the internal circuitry of 741 you could see a lot of transistors wired up in different configurations. So if you measure a floating Vss pin it can show up anything.
I dont think that is a matter to worry, probably you can check the same with a couple of other 741's if you have.
 
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Re: Op-Amp LM741 problem

A lot of integrated circuits have the entire bottom of the chip to be a reverse biased diode. They take that chip bottom and connect it to the most negative voltage the chip will see, such as Vss. If you open circuit the Vss pin, then that substrate diode is not necessarily reverse biased any more. Use the chip the way it is supposed to be, and it will work.
 

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