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From: ftpam1@acad3.fai.alaska.edu (MUNTS PHILLIP A)
Newsgroups: sci.electronics
Subject: Re: cheap hi-speed oscillator
Message-ID: <1990Nov6.212128.16965@hayes.ims.alaska.edu>
Date: 6 Nov 90 21:21:28 GMT
References: <35596@nigel.ee.udel.edu>
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In article <35596@nigel.ee.udel.edu>, hamilton@udel.edu (andrew hamilton) writes...
> 
>Anyone know how to make a cheap variable frequency oscillator that will
>oscillate in the MHz range.  555's don't seem to be able to do more than
>about 500KHz.
> 
>Thanks in advance,
> 
>Andrew.

     Here is one of my favorites.  It should work from less than 1 Hz to several
MHz, depending on the chip used and the resistor and capacitor.  The order of
magnitude of the frequency will be 1/RC.  Stability and spectral purity is not
very good, but it makes a decent digital system clock.

                                     R
                             _____/\/\/\_____
                            |                |
                            |     |\         |
                            |     | \        |
                            |     |  \       |
                            |     |   \      |
                            |     |    \     |
                            |-----|     O---------> Output
                            |     |    /
                            |     |   /
                          __|__   |  /  74C14, 74HC14, etc.
                       C  _____   | /
                            |     |/    Not 74C04, 74HC04, etc.
                          __|__
                          / / /         A TTL 7414 can also be used but
                                        component values are more critical.