| Author |
Message |
Admin |
|
Post subject: Variable Oscillator for Audio Applications
 Posted: Feb 17, 2008 - 11:58 AM
|
|
Site Admin
Joined: Dec 07, 2003
Posts: 455
Status: Offline
|
|
This circuit is paraphrased from an excellent application note4 for the Burr-Brown UAF42 state variable filter. Pin numbers shown are for the UAF42, which I used because it contains precision integrator capacitors, and because it is easily available from Digi-Key. Burr-Brown isn't the only source for analog function circuits. Analog Devices also has a similar line of parts which is available through distribution. Of course, you can breadboard this with any old opamps and capacitors you happen to have available. Parts values shown in parentheses are internal to the UAF42, and would have to be replaced with discrete components if other opamps are used. Opamps like the TL082 and LF353 have performance characteristics similar to the UAF42. With the parts values shown, the circuit will oscillate at around 160 Hz when you set the damping factor slightly negative with VR1. Restore damping factor to zero (VR1 near center of range) to maintain steady oscillation. If you use a 10-turn potentiometer for VR1, you should be able to stabilize output amplitude enough to make a quick distortion measurement. Assuming you aren't at or near clipping, harmonic distortion will be so low as to be unmeasureable.
Oscillator for Audio Applications |
|
|
| |
|
|
|
 |
|
|
 |
Post subject: Please Click to support this site
Posted: Feb 17, 2008 - 11:58 AM
|
|
AdSense
|
|
|
|
|
|
|
Admin |
|
|
|
Post subject: Variable Frequency Oscillators
Posted: Nov 19, 2010 - 09:27 PM
|
|
Site Admin
Joined: Dec 07, 2003
Posts: 455
Status: Offline
|
|
Variable Frequency Oscillators (VFOs)
A stable variable frequency
oscillator can replace a crystal oscillator.
This chapter summarizes what I learned in
my odyssey through six VFO prototypes.
My early VFOs drifted hundreds of Hz and
I got loads of complaints. After I added
temperature compensation, I got the
instability down to 20 Hz drift per minute.
Some stations notice 20 Hz drift and a few
even told me about it. Eventually I built a
super-regulated power supply for the VFO
and got the drift down to about 5 Hz. I
suggest you avoid embarrassment and
work directly toward 5 Hz. According to
the ARRL handbook, +/- 5 Hz is about as
good as you can do without phase lock
loop technology.
Variable Frequency Oscillators |
|
|
| |
|
|
|
|
|
|
|
|
FAQ
Search
Register
Log in to check your private messages
Log in
