|Two Sinus Generators|
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Report by Stefan Spännare, August 2001, updated January 2004
The report can be downloaded below.
To make electronic sinus wave generators with good properties is not a very easy task.
Different methods to avoid distortion from higher order harmonics exist, and also methods
to reduce noise of order 100 Hz from the surroundings and possibly also the power supply.
In this report two sinus wave generators are described, one designed by K. Johansson
(modified Wien bridge) and one based om the integrated circuit ICL 8038. Circuit layouts
are available with the authors comments and changes. An evaluation of the spectral properties
of the generators is also present including oscilloscope views of signals and spectrum.
The modified generator by K. Johansson has a very low THD (Total Harmonic Distortion) of
less than 0.05 % in the frequency range 300 Hz to 30 kHz and has very small even high order
harmonics. It is somewhat sensitive to cooling in the lamp in the Wien bridge wich makes
distortion high at frequencies less than 300 Hz.
The ICL 8038 generator has relativley high high order harmonics and has a THD of about 1 %
in the frequency range 300 Hz to 10 kHz and somewhat higher outside this range.
The results show that the modified sinus generator by K. Johansson has much better spectral
properties than the ICL 8038 generator in the range 300 Hz to 30 kHz. On the other hand the
ICL 8038 can also produce triangle and square wave signals and it is also able to produce
signals at very low frequencies below 1 Hz.
The sinus generator by K. Johansson above and ICL 8038 below.
This image is not present in the report.
Some useful data sheets (mostly from ELFA) to download:
Some useful Internet links: