SeanHatch
New Member
Oscillator Design (Phaser project)
Hi, I am designing an oscillator. The output voltage will control the resistance of 4 JFETs.
This is the first thing I've ever designed really from scratch, so if its totally a horrible design you should say so.
**Anyway I don't have the values all picked out yet.** The values listed for all of the components are simply a product of copy/pasing. I pretty much would like to see if this idea is feasible before I start really getting into it. I have however, done some basic testing in PSpice and the results are promising.
I used a filter on the output of the phase shift oscillator because I need the signal to be smooth, but I also need a fast set time. I can achieve a fast set time with a big Rf in the phase shift oscillator circuit, but the output signal is very distorted. I used the filter to attenuate the harmonics. It works nicely, according to Pspice.
The JFETS I'm controlling will have gate voltages between -0.8 and -3 volts. I used the pair of inverting/noninverting amplifiers like I did because I want 2 of the JFETS to be at -0.8 Volts while the other two are at -3 volts. I hope this makes sense.
Right off the bat I'm pretty sure I can knock out one of the op amps by using a Chebyshev filter. The butterworth filter cannot provide a gain of less than 1, and the output from the PSO is always of a greater amplitude than needed (maybe I can power the PSO's op amp with less than +/-15 volts). THe trouble is is that I'm not all that good at designing Chebyshevs.
Also, I hvae the following problem: The magnitude of the output of the filter changes as the PSO changes with frequency (as in 0.2 and 1.75 Hz). I can't think of a good way to regulate the peak voltage, so I think I'm just going to make some comprimises.
Thanks for reading this!
and thanks for your help!
Hi, I am designing an oscillator. The output voltage will control the resistance of 4 JFETs.
This is the first thing I've ever designed really from scratch, so if its totally a horrible design you should say so.
**Anyway I don't have the values all picked out yet.** The values listed for all of the components are simply a product of copy/pasing. I pretty much would like to see if this idea is feasible before I start really getting into it. I have however, done some basic testing in PSpice and the results are promising.
I used a filter on the output of the phase shift oscillator because I need the signal to be smooth, but I also need a fast set time. I can achieve a fast set time with a big Rf in the phase shift oscillator circuit, but the output signal is very distorted. I used the filter to attenuate the harmonics. It works nicely, according to Pspice.
The JFETS I'm controlling will have gate voltages between -0.8 and -3 volts. I used the pair of inverting/noninverting amplifiers like I did because I want 2 of the JFETS to be at -0.8 Volts while the other two are at -3 volts. I hope this makes sense.
Right off the bat I'm pretty sure I can knock out one of the op amps by using a Chebyshev filter. The butterworth filter cannot provide a gain of less than 1, and the output from the PSO is always of a greater amplitude than needed (maybe I can power the PSO's op amp with less than +/-15 volts). THe trouble is is that I'm not all that good at designing Chebyshevs.
Also, I hvae the following problem: The magnitude of the output of the filter changes as the PSO changes with frequency (as in 0.2 and 1.75 Hz). I can't think of a good way to regulate the peak voltage, so I think I'm just going to make some comprimises.
Thanks for reading this!
and thanks for your help!
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