Question about VCO in a real circuit

[svensl]

VCO question

I am a little confused about VCO's and their bevaviour. Hopefully someone can clarify some of my questions. In general we have the frequency of the VCO that is given by w(out)=w0+Kvco*Vin. The frequency is then being integrated (model) to obtain the phase. We know that the higher the input voltage the faster the VCO accumulates phase and the faster the output waveform frequency. This is a nice mathematical model but I cannot make the connectoin to a real circuit.

1) Using for example N-stage ring oscillators where is the internal phase? Is it a signal I can see and plot in a circuit simulator? If so, is the phase a voltage, i.e. what unit does it have?

2) How is the output signal being generated. Often in books, it is said that the VCO output could be a sine, or pulse wave? How in an actual circuit can I realize this?

I hope someone can help me with this.
Thanks
Svensl

 

[cswang]

Re: VCO question

I am a little confused about VCO's and their bevaviour. Hopefully someone can clarify some of my questions. In general we have the frequency of the VCO that is given by w(out)=w0+Kvco*Vin. The frequency is then being integrated (model) to obtain the phase. We know that the higher the input voltage the faster the VCO accumulates phase and the faster the output waveform frequency. This is a nice mathematical model but I cannot make the connectoin to a real circuit.

1) Using for example N-stage ring oscillators where is the internal phase? Is it a signal I can see and plot in a circuit simulator? If so, is the phase a voltage, i.e. what unit does it have?

2) How is the output signal being generated. Often in books, it is said that the VCO output could be a sine, or pulse wave? How in an actual circuit can I realize this?

I hope someone can help me with this.
Thanks
Svensl

1.internal phase could be happen in any phase , depond on your initial start-up phase, but it is not very important
2.VCO output, it is a sine, or pulse wave naturelly.

 

[svensl]

Re: VCO question

I am not sure what you meant by your answer. I will refine my question. What and where is the phase in a circuit implementation of a vco? For example, I want to generate a pulse whenever the internal phase crosses a certain value. How can I achieve this? Any ideas.

Thanks