Topic 4: Switching Circuits

Question 1

What is a npn transistor?

Answer 1

• Three connecting leads: emitter, base and collector

Question 2

What is the off region of the transistor voltage transfer characteristic?

Answer 2

Top flat part
- Vɪɴ is between 0 and 0.7V
- When transistor is off, no current flows between base-emitter junction or collector

Question 3

What is the linear region of the transistor voltage transfer characteristic?

Answer 3

• Vɪɴ increases above 0.7V and base current starts to flow
• Larger amplified current to flow through the collector and load

Question 4

What is the saturation of the transistor voltage transfer characteristic?

Answer 4

• When Vɪɴ increases, point reached where it no longer causes any change
• Saturated, flat bottom line

Question 5

What is a MOSFET?

Answer 5

• Metal Oxide Semiconductor Field Effect Transistor

Question 6

What are the leads of a MOSFET?

Answer 6

• Gate
• Drain
• Source

Question 7

What is a voltage comparator?

Answer 7

• Converts slow changing signals into fast changing signals
• Inverting Input (V-)
• Non-inverting Input (V+)
  If V+ > V- then Vᴏᴜᴛ will be positive
  If V- > V+ then Vᴏᴜᴛ will be negative