# Extracting information from a Bode Plot (PM, GM, etc...)

• Waxterzz
In summary, the conversation is about a unity feedback system and the extraction of various data including DC Gain, bandwidth, GBW, unity frequency, phase margin, and gain margin. The speaker is seeking instructions on how to solve the problem and presents a possible solution for the DC Gain. The speaker also mentions stability and feedback, and asks for clarification on definitions. A resource is provided for further understanding.
Waxterzz
Hi all,

1. Homework Statement

http://imgur.com/kqZK1Vv

This is the loop gain (A.F.) of unity feedback system.

I need to extract

DC Gain
Bandwidth
GBW (is GBW Gain Bandwith ?)
f unity (I suppose this is unity frequency)
Phase Margin
Gain Margin

What is the optimal PM and f2/GBW for time and frequency domain applications?

## Homework Equations

Don't know => this is not really homework as such, plus in the books I got about electrical engineering not much is said about stability and feedback...

## The Attempt at a Solution

U guys don't need to solve this for me,

What I want is instructions how I can solve it, since I truly have no material about this topic, then I shall try and present it, and you guys can help me furtherKind Regards.

DC Gain =>

80 = 20 log | DCGain |

So DC Gain = 10^4 = 10000

Is this correct?

Waxterzz said:
DC Gain =>

80 = 20 log | DCGain |

So DC Gain = 10^4 = 10000

Is this correct?
Yes.
Next: bandwidth?

Loop gain for a unity feedback system is identical to the open-loop gain of the amplifier.
Hence, you have nothing to do than to apply the definitions of the various data you are interested in.
Normally, the "bandwidth" is identical to the 3dB-Bandwidth.
Stability margins can easily derived by using the appropriate definitions.

Do you know all the definitions?

## 1. What is a Bode plot?

A Bode plot is a graphical representation of the frequency response of a system. It shows how a system responds to different frequencies of an input signal, and can indicate the stability and performance of the system.

## 2. What is PM (phase margin) in a Bode plot?

Phase margin is a measure of the stability of a system. It is the amount of additional phase shift that can be applied to the system before it becomes unstable. In a Bode plot, it is the amount of phase shift at the frequency where the gain of the system is 0 dB.

## 3. How is GM (gain margin) calculated from a Bode plot?

Gain margin is another measure of stability, and it is defined as the amount of gain that can be added to the system before it becomes unstable. In a Bode plot, it is the amount of gain at the frequency where the phase shift of the system is -180 degrees.

## 4. What is the significance of the crossover frequency in a Bode plot?

The crossover frequency is the frequency at which the magnitude and phase of the system's transfer function intersect. It is an important point in the Bode plot, as it indicates the frequency at which the system transitions from a high pass to a low pass filter, and can also provide information about the stability and performance of the system.

## 5. How can I use a Bode plot to optimize the performance of my system?

A Bode plot can provide valuable information about the stability and performance of a system, and can be used to optimize its performance. By analyzing the plot, one can identify any issues with the system's frequency response and make adjustments to improve its performance, such as adjusting the gain or phase of the system at certain frequencies.

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