Term 2

Question 1

What is the conduction angle?

Answer 1

The conduction angle is the proportion of the cycle the output transistor is conducting for

Question 2

What is the conduction angle of a class A output stage?

Answer 2

360 degrees

Question 3

What is the conduction angle of a class B output stage?

Answer 3

180 degrees

Question 4

What is the conduction angle of a class AB output stage?

Answer 4

180< angle &laquo_space;360

Question 5

What is it called when two emitter follower circuits are cascaded together?

Answer 5

Darlington pair

Question 6

Draw the block diagram for class D?

Answer 6

1) PWM
2) NPN and PNP
3) LPF
4) load resistor

Question 7

Why is class D theoretically 100% efficiency but in practice not?

Answer 7

• each transistor is either fully on or off so no power dissipation
• PWM switching is not instantaneous and within transition transistors are active

Question 8

What is the equation for noise figure?

Answer 8

NF = 10log [1 + (en² + (in*Rs)²)/(4kTRs)]

where en² = 4kTrbb + 2qVt²/(Ic)

and in² = 2qIc/β

Question 9

How do you find the upper cut off frequency?

Answer 9

Fu = 1/[2πRs ( Cbe + (1+A) Cbc)]

Question 10

How do you find lower cut off frequency?

Answer 10

Fl = 1/[2π(Rs + rin)C]