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LM2907-N: Operating voltage

Part Number: LM2907-N

Hello. Simple question, I think.  What is the lowest operating voltage of the LM2907?  I may be incorrect, but I cannot determine this from the data sheet.  Thank you.

  • Hi Tony,

    Your observation about the LM2907 datasheet is correct; it doesn't directly state the minimum operating voltage. The 7.5 Electrical Characteristics table is written around VCC = 12 VDC, but that certainly isn't the minimum.

    Datasheet Typical Characteristics Figure 3 - Total Supply Current, Figure 7 - Tachometer Currents I2 and I3 vs Supply Voltage,  and Figure 8 - Tachometer Currents I2 and I3 vs Temperature, all have a lower end scale of 6 V, or a 6 V curve. Figure 18 - Speed Switch application, shows a supply of 6 to 24 V. Therefore, characterization and application of the LM2907 was performed with a 6 V supply. That appears to be the minimum usable supply level for the LM2907.

    If you should use the LM2917 its internal zener voltage is about 7.5 V, and the supply would have to be greater than 7.5 V to bias the zener on. Otherwise, the zener would remain off with a supply less than 7.5 V.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • Hi Thomas. Thanks for replying. I should have been more mindful of the curves in the data sheet. It is such a straight forward part to use.