LM2904: gain margin and phase margin

Shu-Cheng LIN

Guru 11785 points

Part Number: LM2904

Hi Sirs,

Sorry to bother you.

We have use LM2904 to control FAN speed.

Schematic as below

We would like to do Phase/Gain margin test.

Do you have this test report? or have any experience on this test before?

Thanks!!

0 Ron Michallick over 8 years ago

Shu-Cheng,

I suggest 'breaking loop' at purple box. This separates pin 3 from FAN_PWR_V-

For simulation replace box with this.

For real world testing, Use an injection transformer. Use resistor recommended by transformer supplier

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