Download frequency_effects_lab

Frequency Effects
Name:
GID:
Lab 2:
Granthan University
Date:
1
Frequency Effects
Frequency Effects
INTRODUCTION
What are Bode plots? Use a well labeled diagram to aid your explanation.
Bode plots are graphical representations of frequency response curve of electronic circuits and
are semi-logarithmic graph since the frequency axis is linear (Hz), while the gain axis is
logarithmic (dB).
2
Frequency Effects
3
Calculate the input-coupling circuit and output-coupling circuit low-frequency cutoff points for
the circuit shown below.
EQUIPMENT

<List all devices and meters used>
PROCEDURE
Using Multisim construct the circuits shown below:
Frequency Effects
4
a. Connect the Bode Plotter as shown, and use the setting in the figure. Set the function generator
amplitude to 5mVp and 10Hz.
b. Attach the Tektronix oscilloscope channel 1 to measure peak-to-peak voltage across the function
generator, and channel 2 to measure the peak-to-peak voltage across the load RL. Record both
values in the results section, and use them to calculate the voltage gain in decibel – show ALL
work.
c. How does the calculated voltage gain compare to the midband gain from the Bode plot?
d. Using bode plotter cursor to mark and measure the low and high cutoff frequency, calculate the
bandwidth.
RESULTS
Show all screen shots – that prove all meter readings.
Record measured values and calculations in this section.
Vp-p FG = 10 V
Vp-p RL= 10 V
Frequency Effects
5
Power gain, A(db) = 10log10(Po/Pi) where Pi=power input and Po= power output
Since P=VI=V2/R, then,
A(db) = 20log10(Vo/Vi) where Vi=voltage across the function generator and Vo= Voltage across
the Load RL
A(db) = 20log10(10/10)
A(db) = 20log101 = 20 x 0 = 0 dB
The calculated voltage gain is 0 while the midband gain from the Bode plot is 34.5 dB
Bandwidth = fH - fL
Bw = 28.593MHz – 211.884Hz = 28.593 MHz
What types of applications can this circuit be used in? Explain.
The circuit can be used as an amplifier or a filter since it has a flat frequency response over a
wide range of frequencies (Band pass filter).
CONCLUSION
What did you learn?
I learnt that the frequency response of an electronic circuit varies with the change in input signal
frequency and it shows a the band of frequencies where the output and gain remain constant (
band pass)
Frequency Effects
Gain at bandpass = 34.5dB
6
Frequency Effects
Gain in Output Voltage
7
Frequency Effects
fL =211.884 Hz
8
Frequency Effects
fH = 28.593 MHz
9