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I am using this EEPROM in read mode: http://ww1.microchip.com/downloads/en/DeviceDoc/doc0270.pdf

And am using this transistor: https://www.onsemi.com/pub/Collateral/P2N2222A-D.PDF

I need my EEPROM I/O to be connected to other loads, so I am using the NPN transistor in a switch configuration. However, I am unable to find the max current supplied by the EEPROM so I am unsure if I need to put a resistor in between the EEPROM and Base. (If resistor is too high the current supplied by the EEPROM won't be sufficient to drive the NPN transistor). So do I need a resistor? The load I am attempting to drive is a 555 timer.

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  • \$\begingroup\$ Yes, resistor is needed \$\endgroup\$ – Gregory Kornblum Nov 25 '18 at 13:32
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    \$\begingroup\$ Tip: Put the actual part numbers in the hyperlink. I am using a [2N2222A](https://www.onsemi.com/pub/Collateral/P2N2222A-D.PDF) transistor. It makes the text more legible, your question will read much better and we won't have to follow links to understand your question. Post a schematic of your idea for comment. (There's a CircuitLab button on the editor toolbar and there is a 555 component in the library - although the pin arrangement on it is a bit quirky.) \$\endgroup\$ – Transistor Nov 25 '18 at 13:36
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However, I am unable to find the max current supplied by the EEPROM so I am unsure if I need to put a resistor in between the EEPROM and Base.

enter image description here

I'd assume that the current you can extract from the EEPROM is around the 400 uA level and I would also use a resistor. The resistor value would be chosen on this: -

  • BJT Vbe = 0.7 volts
  • EEPROM output voltage = 2.4 volts
  • Voltage across resistor = 2.4 - 0.7 volts = 1.7 volts
  • Current = 400 uA
  • Resistance in base = 1.7 volts / 400 uA = ~4k3 or above and maybe you can push it down to 2k2 to extract a little more current from the EEPROM output.

If that current isn't enough then use a darlington or MOSFET.

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