Where's The Gold? Part 3 – Transistors, Resistors, Potentiometers, Rheostats

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  • #3024


    Where’s The Gold? Part 3 – Transistors, Resistors, Potentiometers, Rheostats

    In the world of small electrical components, nothing is ever how it seems! What do I mean by that? Life has taught us to use logic in our every day-to-day life, and most of the time that logic serves us well. But now things just got a little harder. As a person of logic when we learn what a ceramic capacitor is, what it does and how it looks, we would think that every time we see that baby blue color and the round disc with 2 leads coming out the bottom that it’s a “no brainier” and toss it in our bucket we have dedicated just for that capacitor. After all, once we get enough of them, we’ll crush them to break up the epoxy shell, separate non-metallic from the metals and process those 2 little shiny metal discs to recover the silver they are made of!

    Only problem is if we are relying on how they look we just might end up with something other than the silver we seek. In the world of small electrical components what you see on the outside is called a “package”, but that’s NOT what determines what the component does. It’s what’s inside that package!

    There are 2 categories of transistors; bipolar junction transistor (BJT) and field-effect transistor (FET). Both categories have several subcategories of transistors under them. For more detailed information and pictures see the .pdf attachment from E-scrap Parts Manual for Transistors that I have attached below.

    **Bipolar Junction Transistor(BJT)BJT’s have 3 legs (terminals)Germanium (more common in the 1950s and 1960s), Indium, Gold. Packages can be made of plastic, glass, metal or ceramics, copper.(choice for demanding analog circuits, especially for very-high-frequency applications, such as radio-frequency circuits, wireless systems, high speed digital logic, amplifiers, temperature sensors and logarithmic converters.)
    **Field-effect transistor(FET)FET’s have 4 legs (terminals)Germanium. Packages can be made of plastic, glass, metal or ceramics, copper (Input Amplifiers in Oscilloscopes & voltmeters, RF amplifiers for FM devices, Voltage Controlled Devices, mixer circuits, low frequency amplifiers, digital circuits, memory devices and many other use)

    Resistors, Potentiometers, Rheostats
    There are too many types of resistors to fully list here. Same with potentiometers and rheostats so I am just going to brush over a few too watch out for. However I have also included the chapter on Resistors, Potentiometers, Rheostats from E-scrap Parts Manual as a .pdf attachment for your download and use. You’ll find more detailed information for these items in that attachment (including pictures)

    **Metal Film ResistorsResistance material is often nickel chrome, but for special applications other alloys are used such as gold with platinum and tantalum nitride (active filters or bridge circuits)
    **Network Array ResistorsIridium, Silver, Platinum, Palladium, Rhenium (computer PCB’s)
    **Wirewound ResistorsSilver(depending on type resistance wire) (often used in circuit breakers or as fuses)
    **Potentiometer(POT)Cheaper POT’s no Rare, Valuable and/or Precious Metals: Higher end POT’s: Gold, Platinum (used in a very wide range of industries and applications, it would be difficult to list all applications)

    Next week – Resistance Temperature Detectors

  • #3283


    Another interesting read. If only I could go back and do things over in school and college. Thanks for helping me expand my horizons.

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