transistor switch

Discussion in 'General Electronics Chat' started by hssucgang, Jul 19, 2007.

  1. hssucgang

    Thread Starter New Member

    Jul 19, 2007
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    is there any transistor switch or relay switch that works on 2 volts?
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Two volts should work pretty much with all standard bipolar junction transistors (BJTs). This is not sufficient voltage to operate a field effect transistor. A darlington BJT transistor would probably not be a good choice.

    hgmjr
     
  3. GonzoEngineer

    New Member

    Jul 8, 2007
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    Try an Optoisolator
     
  4. lightingman

    Senior Member

    Apr 19, 2007
    374
    22
    If you are trying to switch 2 volts with a transistor, remember that the forward voltage drop accross the device is about 0.7 volts.....2 volts will switch a transistor on without a problem, through a resistor (about 2K2) into the base........ Daniel.
     
  5. ashok_ece2006-2010

    New Member

    Jul 19, 2007
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    plz provide the information about "B.L.THERAJA" ELECTRIC CIRCUITS 1 OF 3RD SEM
     
  6. nomurphy

    AAC Fanatic!

    Aug 8, 2005
    567
    12
    Is 2V your source voltage (Vcc), or your drive voltage? In either case, the general answer is, yes.

    As noted above, a general bipolar transistor (2N3904 / 2N3906) only requires ~0.7V on the base-emitter. Some FET's can be used with a lower drive voltage, for example the NTD3055 FET requires a gate voltage of only 2V.
     
  7. nanovate

    Distinguished Member

    May 7, 2007
    665
    1
    If you are going to drive a relay with a bjt you should not forget that you need to have enough current available to go into the base.

    Roughly I_C = I_B * beta
    I usually use beta = 50 for relay drive ckts (for margin) and look at the coil resistance and voltage of the relay to get my I_C. Then calculate the I_B. From this I can size the base resistor accordingly.

    R = (2V-0.7)/I_B

    Using R = 2K2 you can easily drive 30mA of coil current.

    John
     
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