I came up with this circuit when I was in college, and at the time I thought I had figured it out. SgtWookie SPICED it, and I've been using it as a check for trying to calculate what the frequency of the oscillator should be, with no success to date.
http://forum.allaboutcircuits.com/attachment.php?attachmentid=2756&d=1207934728
My original assumtion was the frequency was where the reactance of the caps equaled the resistors, but that doesn't work. Reading the SPICE display I figure the oscillator is around 5 Hz. Calculating from the previous assumption...
R = 470 Kohms C = 0.1 uF
470 Kohms = 1 / (2 * Pi * freq * .1uf)
freq = 1 / (6.28 * 470K * .1uf)
freq = 1 / 0.295 = 3.4 Hz
As you can see, these answers don't jive. An op amp intigrator will shift any frequency to 90 degrees of the input, the output amplitude will vary. I also assume the frequency is more or less indepentent of the power supply, though this is suspect. Any thoughts?
http://forum.allaboutcircuits.com/attachment.php?attachmentid=2756&d=1207934728
My original assumtion was the frequency was where the reactance of the caps equaled the resistors, but that doesn't work. Reading the SPICE display I figure the oscillator is around 5 Hz. Calculating from the previous assumption...
R = 470 Kohms C = 0.1 uF
470 Kohms = 1 / (2 * Pi * freq * .1uf)
freq = 1 / (6.28 * 470K * .1uf)
freq = 1 / 0.295 = 3.4 Hz
As you can see, these answers don't jive. An op amp intigrator will shift any frequency to 90 degrees of the input, the output amplitude will vary. I also assume the frequency is more or less indepentent of the power supply, though this is suspect. Any thoughts?