A Voltage Controlled Oscillator for your lab
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- Опубліковано 1 жов 2024
- A full triangular waveform #VFO is presented and explained in this video.
Unlike the well known 555 IC that can be used also as Voltage Controlled Oscillator, the circuit presented in this video features much better characteristics, both for the range of frequencies (a full one order of magnitude for every single range) and for the quality of the generated waveform, low noise and perfect straight slopes of the triangular wave.
This circuit is the starting point for future developments that will be presented in next episodes, with the aim to achieve a complete instrument for the laboratory of electronics.
For further reading I recommend to read the description of the HP generator Model 3311A presented by Hewlett-Packard in its own publication “Hewlett-Packard Journal” on July 1973. Although the circuit is substantially different from the one showcased in the video, both start from the same concept of charging/discharging a capacitor through a variable voltage source driving a constant current source.
Thanks for the circuit! I really like using triangle and sawtooth waves for making pwm controllers.
I'm curious as to it's intended use? The frequency range is mostly out of hearing so I don't think it's an audio circuit. And there wouldn't be much need to worry about that tiny amount of distortion in an audio VCO design. All my synthesizers have several VCO's and each brand has it's own colored sound.
VCOs are useful for many other applications than just making music or for audio purposes: in sensors, e.g., in capacitive and inductive sensing; as a laboratory/testing equipment. Higher frequencies than audible are useful to test capacitors and inductors, to test electronic circuits and components. However if you watch the whole video you will see that it can work even at audible frequencies and the sound that can be heared is actually picked from the VCO. Indeed the bands will be: .5-5Hz, 5-50Hz, 50-500Hz, 500-5KHz, 5-50KHz, and 50-500KHz.
Thank you for commenting, your question is inspirational to make a video to show this kind of applications.
you have doubled the discharge current in its ramp-down to cancel the constant charging current. can you use a separate transistor to terminate the charging instead? so both charge and discharge can take place in a balanced manner.
Yes but it's more complex and expensive, also it may introduce distortion due to the turn on delay of the transistor.
For this oscillator purpose, what would be a good type of capacitor to use?
Polyester
A great circuit, and well explained. I like the elegant way that you generate and compensate your waveform. You have dusted off many years of memories from when I was doing more electrical engineering work. Thank you for your video! I am going to enjoy the next one.
Great video! Can you please show us modifications needed to make control voltage work in "1V/octave" (increasing CV by 1V doubles the frequency) standard?
Thank you. That requires an exponential pre-conditioning circuit which is usually made exploiting the transfer characteristic of a BJT.
@@AccidentalScience Ok, thank you.
@@CHEpachilo sorry mate, I understand you expected a video but it will take time to go into this topic so I rather gave you a quick answer right in the comment, hopefully driving you to the right path. Cheers.
@@AccidentalScience nevermind that works for me. I prefer ideas over the "instructional" videos.
This is super interesting. I am looking forward to the rest of the videos about this.
More to come!