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QUESTION: LM124 operational amplifier in buffer configuration is powered on with negative supply and input connected to respective pins but positive supply line is kept floating. Can such practice of switching on Operational amplifiers degrade the operational amplifier parameters like input bias current due to internal base-emitter junctions reverse biased? Can it degrade the noise performance of operational amplifier?

ANSWER: Not sure I understand the question. Let me confirm:  You are powering the op amp off and on by removing the dc power line.  Is that right?

If so, your question if this will have a deleterious effect on the op amp I would say not.  It is common way.  However, you should check bias voltages to the LM124 to avoid some current into the chip that could cause overheating by positive conduction.  It would be better if you could disable both plus and minus dc lines, of course.

Another item to look at is if a capacitor charge or discharge when supply voltages are connected which could cause a degrading pulse somehow.  

Does this help?  Cheers.

---------- FOLLOW-UP ----------

Internal Diagram of LM124
Internal Diagram of LM  

Test Circuit
Test Circuit  
QUESTION: The image showing the condition in which op-amp is tested is attached.

Thanks for the clarification.

Yes, I would be nervous about the possible damage to base/emitter junctions.

You could try it on the lab bench and see if you got failures.  I think you could get failures rather soon from junction breakdowns.

Hope this helps.  


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Electronics questions about AC, DC and digital theory.


Graduate electrical engineer with over 40 years in electronic design, manufacturing, project organization and patent review. Experience in fields of industrial and consumer electronics (audio, video, acoustics, etc.)

IEEE (Institute of Electrical and Electronics Engineers); Senior Life member AES (Audio Engineering Society), Fellow Life member

BSEE University of North Dakota

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