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TOPIC: Switch less voltage with an NPN than the control voltage?

Switch less voltage with an NPN than the control voltage? 3 years 7 months ago #17573

  • hop
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I feel stupid asking this but it never occurred to me until I got to this point of a project I'm working on...

Can you switch less voltage with a NPN transistor (2N2222) than the voltage used as a control voltage?

I want to switch on and off 3.3vdc using a 2n2222 NPN transistor using a 5vdc logic level from a MCU. This works great when the load is 12vdc, but never tried it with a voltage less than the control voltage. I guess I could answer this myself by studying how a transistor works, but I thought I would throw this out there and see if I can get some feedback.

Any feedback and advice would be greatly appreciated. I know, LEARN ANALOG ELECTRICITY HOP!

I could just breadboard it and measure, and see what happens, but it's a valid question that I'm sure has been asked by digital savvy prototypers that know little about analog.

Thank you guys for your time!

Switch less voltage with an NPN than the control voltage? 3 years 7 months ago #17576

  • Door Knocker
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With the standard transistor LOAD switching circuit, you can switch down to Milli-volts in place of the 3.3V supply. For your application though it will be perfectly fine the way the schematic depicts.
                                 o--------> LOAD <------< +3.3V Supply
                                 |
                        1k       C
5V Digital Logic >--o--/\/\----- B  <-2n2222
                    |            E
                    |   10k      |
                    o--/\/\------o
                                 |
                                GND  
Last Edit: 3 years 7 months ago by Door Knocker.
The following user(s) said Thank You: hop, W4GNS

Switch less voltage with an NPN than the control voltage? 3 years 7 months ago #17583

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Awesome sir, thank you!! I will post how it works. :)

Switch less voltage with an NPN than the control voltage? 3 years 7 months ago #17584

  • be80be
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There will be a little voltage drop switching like that but most times that's not a problem.
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