ECE492 Section 2 Notes

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Welcome! Notes for Spring 2022 Electronic Circuits course. Will make this more pretty as things evolve.

My goal is to make Electronic Circuits so easily digestible, you could teach a middle schooler. We'll see if this works.

Prologue

Hey how are you. I will insert something here later. :)

Section 2.1

We'll begin by covering a Bi-polar Junction Transistor, also known as BJT.

What is it exactly? Well, it's a transistor.

  • It is a 3 terminal devices.
  • It is a unsymmetrical device.
  • It amplifies the signal.

There are two types of BJTs:

  • NPN, in which...
  • PNP, in which...

Now we'll cover (B) Common Emitter Current gain:

  • 50 < B < 200

...and (Alpha) Common Base Current Gain:

V-I Characteristics of Transistors:

  • AAAA

NPN Transistor Example:

  • Cut Off: Both junction are reverse biased.
  • Saturation: Both junction are forward biased.
  • Active: One junction is forward biased, another one is reverse biased.

Understanding cut off regions for NPN transistors:

  • Cut off region (open switch - both junctions one reverse biased)
  • Saturation region (closed switch)
  • Active region (amplification - one junction forward biased another is reverse biased)
  • Breakdown region (Damaged - acts like open circuit essentially)

How do you know when one of these three (or four counting breakdown) apply?

  • Voltage
    • VE < VB < Vc
    • VE < VB > Vc
    • VE > VB < Vc
    • VE > VB > Vc
  • NPN
    • Active
    • Saturation
    • Cut off
    • Reverse active
  • PNP
    • Reverse active
    • Cut off
    • Saturation
    • Active

Understanding common emitter (CE) configuration

  • Consider the following configurations...

Consider the following example:

  • We'll assume that VB is equal to 0 (since it is grounded).
  • Start solving the example by assuming active mode of operation.
  • In active mode of operation
    • BBE = 0.7 (NPN), BCE >= 0.3V
    • BEB = 0.7 (PNP), BEB >= 0.3V

Therefore, VEB = 0.7V = VE - VB such that VB = 0


Header 2

It sometimes allow current, and sometimes it doesn't.


Assignment 1.1

We'll take this and plug it into to find x2: