ECE Undergraduate Laboratory
ECE 371 - Electronic Circuits Design

ECE 371 - Electronic Circuits Design

Lab 3: Signal Generators

OBJECTIVES

Lear to generate outputs with no input signal applied to the circuit. You will do so by generating a rectangular pulse train using a 555 timer, and a sinusoidal output using a Wien-Bridge oscillator.


PRELAB

Simulate the three circuits presented in this lab experiment using your own specs which you specify before you choose the appropriate components (Make sure the specs are chosen before you choose the component values. You will in your report have to justify your choices of component values once the specs are set. Write about the usefulness of the diode used in the 555-based astable multivibrator.


References

S. Franco "Design with Operational Amplifiers and Analog Integrated Circuits", McGraw-Hill 1988. Chapter 8.

Lecture Notes


LABORATORY

You are the designer and the client. You need to set the specs and then figure out which components will make your design viable through some calculations, simulation, and then an implementation to confirm your work. Do not use these sample circuits as the circuits to implement.


  1. 555-Based Astable Multivibrator (Free Running)


    Figure 3.1.1  555-Based Astable Multivibrator
    Figure 3.1.1: Figure L3.1 555-Based Astable Multivibrator

    Design an astable multivibrator and look at all the characteristics of the output signal, such as the level, the frequency, the duty cycle and confirm using a table made of the values from the calculations, the simulation, and the implementation.

    Discuss the need for the diode, and what and how it affects the output characteristics.


  2. 555-Based Monostable Multivibrator

    Design a monostable multivibrator and look at all the characteristics of the output signal, such as which state is stable, and which is not (one stable state). Decide the duration of the unstable state and present an application for which the monostable multivibrator will be suitable. Research how circuits need to be modified for very long unstable state.


    Figure 3.1.2  555-Based Monostable Multivibrator
    Figure 3.1.2: Figure L3.2 555-Based Monostable Multivibrator

  3. Wien-Bridge Oscillator

    Choose a different frequency for this Wien-Bridge oscillator keeping in mind that you are constrained by the components values you may have available. A fast switching diode will be required for the proper operation of this circuit. 10% extra credit if you can present a functioning implementation.


    Figure 3.1.3 Wien-Bridge oscillator
    Figure 3.1.3: Figure Figure L3.3 Wien-Bridge oscillator


REPORT

Present all relevant calculations, schematics, and measurements. Describe briefly how the circuits you tested work. Do the measured frequencies and waveform agree with expectations? Include all observations on the circuits performance and if possible give explanations.