Basic electronics stuff

Some notes on basic electronics stuff. Derived mostly from Wikipedia articles.

Band gap

Valence electron

Conduction electron

Electron holes

Diode

Extrinsic semiconductor

Intrinsic semiconductor

Charge carrier

Fermi level (of a solid state body)

Amount of thermodynamic work that needs to be done to add an extra electron to that solid-state body.

Depletion region

p-type semiconductor

n-type semiconductor

p-n junction

Transistor

Obtain a controlled flow of electrons.

—

Bipolar Junction Transistor (BJT):

         Emitter
    /
Base---|
    \
         Collector

Base regulates the flow from emitter to collector.

—

Field Effect Transistor (FET):

         Source
    /
Gate---|
    \
         Drain

PLA

Digital logic families

Diode Resistor Logic (DRL)

  • Construction of Boolean logic gates with diodes.
  • Popular in early computers.
  • Not all logic gates can be constructed only with diodes. Only AND and OR.
  • Advantage: Simple.
  • Disadvantage: Lack of an amplifying stage in each gate (so DRL normally limited to single stage?)

Resistor Transistor Logic (RTL)

  • Input network = resistors
  • Switching done by BJTs
  • Earliest class of 'transistorized' digital logic circuit.
  • First digital logic family to be produced as an IC.

Diode Transistor Logic (DTL)

  • Uses diodes and invertor logic (ie, NOT).
  • Direct ancestor of TTL.
  • Came after RTL.
  • Logic gates with diodes and amplification via transistors

Transistor Transistor Logic (TTL)

  • Built from BJTs.
  • Transistors are used to do both the logic function and the amplifying function.
  • TTL ICs were used to build computer processors before the advent of VLSIs.

Field Effect Transistor (FET)

MOSFET

Metal-Oxide Semiconductor Field-Effect-Transistor

Bipolar Junction Transistor (BJT)

Impedance (in electronics)

High impedance

  • Allows lesser amount of current to flow through in relation to the applied voltage.
  • High impedance circuits are low current and (potentially?) high voltage.
  • Tristate in digital circuits => neither high state nor low state. Effectively an open circuit.
    • Basis of bus systems in computers.

Low impedance

  • Low impedance circuits are high current and low voltage.

7-segment display

Basically a bunch of LEDs bundled together.

      a
   -------
  |       |
f |       | b
  |   g   |
   -------
  |       |
e |       | c
  |       |      
   -------     ---
      d         p

Possible configurations:

Got to use a multimeter to see which type of 7-segment display it is.

| n | a | b | c | d | e | f | g | p |
|---+---+---+---+---+---+---+---+---|
| 0 | 1 | 1 | 1 | 1 | 1 | 1 |   |   |
| 1 |   | 1 | 1 |   |   |   |   |   |
| 2 | 1 | 1 |   | 1 | 1 |   | 1 |   |
| 3 | 1 | 1 | 1 | 1 |   |   | 1 |   |
| 4 |   | 1 | 1 |   |   | 1 | 1 |   |
| 5 | 1 |   | 1 | 1 |   | 1 | 1 |   |
| 6 | 1 |   | 1 | 1 | 1 | 1 | 1 |   |
| 7 | 1 | 1 | 1 |   |   |   |   |   |
| 8 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |   |
| 9 | 1 | 1 | 1 | 1 |   | 1 | 1 |   |

There is also:

Arduino Uno

Arduino uno uses an ATmega microcontroller.

(Hadn't known that microcontrollers are sometimes referred to as 'MCU's, which stands for Micro-Controller Unit.)

        +--------+         
        |        |                
        |        |-- D19          
        |        |-- D18          
        |        |-- AREF
        |        |-- GND
        |        |-- D13          
IOREF --|        |-- D12          
RESET --|        |-- D11          
+3.3V --|        |-- D10          
  +5V --|        |-- D9           
  GND --|        |-- D8           
  GND --|        |                
  Vin --|        |-- D7           
        |        |-- D6           
   A0 --|        |-- D5           
   A1 --|        |-- D4           
   A2 --|        |-- D3           
   A3 --|        |-- D2           
   A4 --|        |-- D1           
   A5 --|        |-- D0           
        +--------+

A0-A5 are analog pins. (ADC, Analog to Digital, at 10 bit precision actually. So ranges in [0,1024) integer interval.)

Doubts:

Links:

PCB

Printed Circuit Board

Terms:

Layers of a PCB

Outermost to innermostʳ:

  1. Substrate
    • An insulator.
    • Can separate two conducting layers in case of multi-layer PCBs
    • Could be made of fibre glass. Or of paper (eg: FR1ʳ)
  2. Copper layer
    • The conducting part.
  3. Soldermask
    • Made of resin?
    • Responsible for the usual green colour of PCBs.
  4. Silkscreen
    • Contains labels for easy identification.

THT vs SMT

Ways of placing components onto the taped out PCB.

  • Through-Hole Technology
    • Considered obsoleteʳ
    • Holes are drilled in PCB and component is soldered after inserting the pins through these holes.
  • Surface-Mounted Technology
    • Surface mounted device (SMD)
    • There are pads on to which pins of components are placed. No holes need be drilled onto the PCB.
    • Better than THT in most aspects. Cheaper, more accurate.

Fiducial marker

  • For helping 'pick-and-place assembly machines'
    • ie, assembly of components onto the PCB being done by a machine.
  • Especially common for square or rectangular designs
  • Global fiducials: Usually place in diagonally opposite corners
  • Local fiducials: Place at a particular point ʳ

Links:

Other electronic stuff of interest