Design Project: Signal generator
Explain the principle of operation for the particular integrated circuit you are using in your signal generator device. How does it function, internally? Explain how it produces each of the following wave-shapes:
- Triangle wave
- Square wave
- Sine wave
This question provides an excellent opportunity for students to research their chips' datasheets, and to comprehend what engineers have written there.
Explain how frequency is adjusted in your signal generator circuit. Your circuit should contain both a "coarse" and a "fine" adjustment (the coarse adjustment could be a multi-position switch, to select different frequency ranges).
Students should be able to find this information in their chips' datasheet(s).
What provisions are provided on the integrated circuit for adjusting the distortion of the sine wave output? Explain how you would determine when the sine wave output was properly adjusted (for minimal distortion). What test equipment would be ideal to use for this purpose, and how would that test equipment be set up on your circuit?
Professional-quality spectrum analyzers may not exist in your lab, but do not worry. There are several high-quality devices built to interface with a personal computer that are capable of displaying spectrum analyses. If all you care about is low frequency (audio range) analysis, you can even get away with using a personal computer sound card (with the appropriate software) as the analysis device.
Suppose you needed to boost the power output of your signal generator to 10 watts. This is substantially more than what the integrated circuit is capable of delivering unassisted. What else would you have to add to your circuit in order to obtain this level of power output? What difference(s) will it make to your design if you only intend to operate at audio frequencies, versus if you intend to sweep from audio frequencies all the way up to IF or even RF?
Students will have to consider several different factors when choosing an appropriate amplifier for the task, bandwidth being just one of them. Adding an amplifier stage to the signal generator circuit is a very appropriate design objective to include in this project, by the way!