# ECE492 Section 3 Notes

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 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

• 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:

• $B={\frac {I_{c}}{I_{b}}}$ • 50 < B < 200

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

• $Alpha={\frac {B}{B+1}}={\frac {I_{c}}{I_{e}}}$ We'll take this $x_{3}={\frac {9}{3}}$ and plug it into $2x_{2}+x_{3}=5$ to find x2:
{\begin{aligned}2x_{2}+x_{3}=5\\x_{3}={\frac {9}{3}}\\{\text{Plug in }}x_{3}={\frac {9}{3}}{\text{ into }}2x_{2}+x_{3}=5{\text{:}}\\2x_{2}+{\frac {9}{3}}=5\\2x_{2}=2\\x_{2}=1\end{aligned}} 