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audioguru said:Now you have a very fast current-feedback opamp with a high output current. But the level stabilizing diodes are clipping the top and bottom of the waveform.
If you reduce the opamp's gain to be only slightly higher than 3.0 then the distortion will be reduced but the oscillator will take a long time to reach its final output level and one day might not work.
audioguru said:If you remove the diodes then the output will increase until the output of the opamp clips.
There are many high frequency oscillators that use tuned LC circuits to make a sine-wave. I think some oscillators with a quartz crystal have a sine-wave.
I made a low distortion sine-wave oscillator as a phase-shift type.
A resistor in series then a capacitor to ground creates a lowpass filter with a 60 degrees phase shift. It is buffered with an opamp then feeds another and another to make a total of 180 degrees phase shift. The last one is buffered and is the low distortion output which is inverted by a 4th opamp that clips and feeds the input.
The 3 lowpass stages reduce the clipping distortion to nearly nothing.
The lowpass filters have a little amount of loss that can be made up if the opamps have a little gain.
audioguru said:My portable oscillator was for audio frequencies and used ordinary but pretty fast MC33077 dual opamps. The schematic is stuck on the broken hard drive of my old 486 computer.
Texas Instruments have a phase-shift oscillator for 2.8kHz that has a low output level because its buffer opamps don't have any gain.
audioguru said:1) The MC33077 cannot drive a load resistance as low as 100 ohms. Try a minimum of 1k ohms.
2) Its max full output frequency is 200kHz but your RC has a phase shift of 60 degrees at about 1.5MHz. Try much higher value capacitors for a lower frequency then increase the frequency after you get the oscillator working.
3) Each 60 degrees of phase-shift reduces the level by about half. So the gain of the inverting opamp needs to be a little more than 8.