Lecture 16

Question 1

What is the bandwidth

Answer 1

The frequency at which the frequency reponse is 3dB less than at low freq

Question 2

If the term in the characteristic equation is squared of a term on the data sheet what should you change

Answer 2

Taking logs so squared turns into multiply by 2, therefore double the slope

Question 3

What is the gain margin,

Answer 3

Amount of additional gain in dB that could be tolerated before the system becomes unstable

Question 4

What is the phase margin

Answer 4

Amount of additional phase that can be tolerated when the gain is 0dB

Question 5

How do you calculate the phase margin

Answer 5

Find the frequency at which the magnitude is at 0dB then on the phase bode diagrams at this frequency check the difference between the phase and 180 degrees

Question 6

How do you calculate the gain margin

Answer 6

On the phase bode diagram, find the frequency at which the phase = 180, at this frequency on the gain bode diagram, find the difference between the gain and 0dB

Question 7

How do you know if a system is unstable based on a bode diagram

Answer 7

If on the magnitude bode diagram the gain is more than 0dB, and if on the phase diagram the phase is less than -180 degrees