Current Controlled Oscillator Design (Help Needed)

how to design current starved ring oscillator

Dear all,

I'm about to enter my final year of studies which would require me to take on a final year project.

As a matter of fact, I have interest in the field of analog IC designing and I perfectly understand that this demands great amount of self-reading and exploration which is something that I'm prepared to go for.

As of now, I'm given a list of projects, from which I saw an area of interest that
caught my attention. And that's Current Controlled Oscillator Design. Sadly, I do not have much knowledge in this and I would like to know more starting from the basics. I have tried goggling but due to my limited capability, I could only source
for technical papers which assume the readers to have certain fundamental knowledge in that area.

So, I'm really hoping for some help from the experts in here. Can I have some
directions to read up everything about the basics of a Current Controlled Oscillator Design.

Sincerely appreciate any help and support given.

Regards

current controlled oscillator

sk.shawn said:

Current Controlled Oscillator Design.

Click to expand...

Read about and use a Controlled Current Source (CCS), by which you charge a capacitor. Use a Comparator to detect a certain maximum voltage at the cap, and use its output signal to discharge the cap (either fast by a simple MOSFET switch, or more slowly by the original or a 2nd CCS). The output of the Comp is your Oscillator output.
Have fun! erikl

current controlled oscillator

Hi erikl,

Many thanks for your reply. Do you know where I can read more about CCS? And
any online resources or book you would recommend?

Thanks once again for your help. Appreciate it!

Regards

current starved ico

Hi Shawn,
As erikl suggested you can use the idea of generating a ramp and comparing it with a reference to generate a clock (oscillations).
You can also generate a clock using a current-starved ring oscillator (ICO). You can refer to Jacob Baker's book "CMOS Circuit design, Layout and SImulations".

Regards,
RDV

linearity current starved oscillator

sk.shawn said:

Hi erikl,
Do you know where I can read more about CCS? And
any online resources or book you would recommend?

Click to expand...

Hi shawn,
you can find out about constant current (CC) sources (CCS) practically in every book about electronic design, e.g. also in Baker's book mentioned by RDV above, or e.g. these low-power CCS's on pp. 14 & 15 of Vittoz' lecture (below). In order to control these CCS's, you can either control analogically their reference, or their output by digitally selecting CC output transistors adding their currents in parallel.
Cheers, erikl

current control oscillator

Wow thanks Eric! Appreciate it.

Was wondering if you have any knowledge on voltage controlled oscillator designs for high linearity? Are you able to recommend a good book or any online resources for me to start the basics from? Or perhaps I can find this information from Jacob Baker's book "CMOS Circuit design, Layout and SImulations"?

Sorry for the trouble.

Thanks once again for your help.

Regards

Added after 2 minutes:

ravirajdv said:

Hi Shawn,
As erikl suggested you can use the idea of generating a ramp and comparing it with a reference to generate a clock (oscillations).
You can also generate a clock using a current-starved ring oscillator (ICO). You can refer to Jacob Baker's book "CMOS Circuit design, Layout and SImulations".

Regards,
RDV

Click to expand...

Hey thanks for the information provided.

Cheers

current controlled oscillators basics

sk.shawn said:

... knowledge on voltage controlled oscillator (VCO) designs for high linearity? Are you able to recommend a good book or any online resources for me to start the basics from?

Click to expand...

First and foremost this depends on the frequency range you need. If you search this forum and/or the parallel forum "Analog Circuit Design" or Google Books for, e.g., "cmos vco", you'll probably find most results on very high frequency (VHF) VCO's, mainly in the >1GHz domain. So I suggest you first make a selection on your required frequency range. You'll still get a lot. After this, you could narrow down your selection by limiting the search with additional words like, e.g. "high & linear", if you need such.

sk.shawn said:

Or perhaps I can find this information from Jacob Baker's book "CMOS Circuit design, Layout and SImulations"?

Click to expand...

Don't own this book, but I'm sure you'll find basic info about CCS's and VCO's in every (modern) book about electronic design.

Cheers, erikl

Hi Eric,

Thanks for the valuable words. I will refine what is exactly needed out of the VCO which I may work on later.

Will post questions in here again if I have any.

You guys are great. Thanks for the help!

Cheers!