who here can ecplain transistors?

Discussion in 'OT Technology' started by multiplexor, Jan 3, 2002.

  1. multiplexor

    multiplexor Intellectual

    Sep 12, 2001
    Likes Received:
    Montreal Quebec Canada
    who here can explain transistors?

    i'm very amateur at this electronics thing, but i can pick it up decently quickly.

    i've known about resistors and how to use them forever, i've started using capacitors, and now i need to learn how to use a transistor.

    what's the diff between a bipolar, (JETT or FETT?), MOSFET, NPN, PNP?

    i'm trying to design a simple circuit that would make a led fade for a period of 4-5 seconds. Right now i'm using 30,000uF large capacitors(3x10,000uF). I was told that i can use a really tiny capacitor and a transistor.

    the circuit uses 3 volts, and i need to power 4 LEDS. leds are 3 volts each at 20mA each.

    Any help would be aweseome Thanks.
  2. EkriirkE

    EkriirkE Zika Xenu OT Supporter

    Jan 11, 2004
    Likes Received:
    Dublin & San Francisco, CA
    For that design, you could just use a simple NPN or PNP... you can get a pack of ~15 at radioshack for cheap. They are sometimes called "Switching Transistors"
    I haven't really looked into *FET types, but I know NPN/PNP. Basically, they take a tiny input to trigger a larger throughput. Like a relay, or a diode that had to be activated. These have 3 pins, the Base, Emitter and Collecter.
    In a NPN, you can hook the E to negative, the C throught to your circuit, and B throught a resistor and capacitor in series to positive.
    A PNP has just the opposite polarities. E to positive, C to the pos end of your circuit (taking negative), B through the cap/res to neg.
    The B(ase) can function on your circuit's power from the E(mitter), or you can trigger it from another power source/circuit by connecting the proper polarities to B and E.
  3. striker754

    striker754 Chillin

    Dec 13, 2001
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    transistors are really just 2 diodes with one end hooked together.

    its similar to a relay. apply voltage on the base (middle) terminal and the outer two slowly begin to "connect" to each other. Current flow through the collector and emitter is dependant on the power at the base.

    Think of it as a water valve, the more you turn the valve, the more water that flows. The more power you apply to the base, the more that can flow in the collector and emitter

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