LM124A: LM124A : INPUT VOLTAGE RANGE PROBLEM

seyong park

Prodigy 30 points

Part Number: LM124A
Other Parts Discussed in Thread: LM124

HELLOW,

I HAVE A QUESTION ABOUT THE LM124A.

I HAVE ONLY POSITVE 15V POWER SUPPLY TO LM124 ON NO.4 PIN & NO.11 PIN TIED ON GROUND.

BUT, NO.3 PIN INPUT VOLTAGE RANGE FROM NEGATIVE 10V TO POSITIVE 10V.

IS IT POSSIBLE THIS APPLICATION?

I HAVE WORRIED ABOUT LM124 OP-AMP DAMAGE OR OTHER PROBELM OCCOUR.

THE DETAILED SCHEMATIC IS SHOWN BELOW.

over 5 years ago

0 kai klaas69 over 5 years ago

Guru 140200 points

Hi Seyong,

yes, this presents a problem. The input voltage must not go more negative than the voltage at pin 11. See section 6.1 of datasheet.

Kai

0 Kirby Kruckmeyer96848 over 5 years ago

TI__Genius 17115 points

Hello Seyong,

This is not a permissible condition and will damage the part if the current is not limited.

TI has many versions of the LM124 which are covered by different datasheets, so I am not sure which you are using. But, in any case, the abs value for the input pins shown in all datasheets is -0.3V. This is for Vcc- at ground. In reality, the abs max is -0.3V lower than the Vcc- pin (which of course is -0.3V if Vcc- is grounded). Any voltage lower than this will start to turn on a diode and cause excess current flow.

0 seyong park over 5 years ago in reply to Kirby Kruckmeyer96848

Prodigy 30 points

Thank you very much.

0 seyong park over 5 years ago in reply to kai klaas69

Prodigy 30 points

Thank you so much.

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LM124A: LM124A : INPUT VOLTAGE RANGE PROBLEM