ECE492 Section 3 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.


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

Section 3.1

What is a MOSFET?

  • Stands for: Metal Oxide Semiconductor Field Effect Insulator.
  • Yay!

See Figure 3a.

Has 3 sides:

  • Gate, Drain, and Source
  • The gate current is always 0 (Ig = 0).
  • It is a symmetrical device (drain as source and vice versa).
  • Length of channel is typically 0.03um to 1um
  • Width of channel is typically 1um to 100um.
  • Gate current is typically 0mA (10^-15mA)
  • Drain voltage in position...

Threshold Voltage (Vt)

  • At which a sufficient number of mobile electrons accumulate in the channel region to form a conducting channel.

Effective Voltage (or Overdrive Voltage)

  • Vov = Vgs - Vt

Additional formulas to consider:

  • Kn' = UnCox = Process Transconductance Parameter
    • Un = Electron mobility
    • Cox = Oxide capacitance
    • Kn = MOSFET transconductance parameter = Kn'[w/L]
  • r_DS = Channel Resistance = [1/g_DS] = [1/[UnCox][w/L][Vgs-Vt]]
  • At V_DS, the channel is going to be deepest at the source and shallower at the drain.
  • Channel resistance is inversely proportional to the gate voltage.
  • Channel pinch off:
  • The zero depth of the channel at the drain ends because of V_DS = V_GS - V_E
    • If V_GS < Vtn then no channel, so transistor is working in cut off region (I_D = 0)
  • MOSFET operation
    • Tniode region
    • Saturation region

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

  • 50 < B < 200

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

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: