ring oscillator looking for square wave

Thread Starter

daanmicro

Joined Nov 15, 2017
50
Hi there,

i'm devoloping a ring oscillator using MOSFET's for a specific application. Doing this, i can create the following signal:



Now i want to convert this signal to a square wave signal. Is this possible with only PMOS transistors and resistors? If so, can anybody help me to achieve this?

Thanks in advance!!
 

DickCappels

Joined Aug 21, 2008
7,273
Make or buy a Schmitt trigger and connect the input of the Schmitt trigger to one of your ring oscillator's outputs. I am confident that you can make a PMOS-only Schmitt trigger but I don't know how.

If you make ring oscillator out of an odd number of Schmitt triggers you will automatically get square waves on the outputs.
 

Thread Starter

daanmicro

Joined Nov 15, 2017
50
Alright thanks! I indeed already read something about the schmitt trigger. But i don't know how to build it out of PMOS either, im gonna look further but thanks again!

By the way, can't buy any components as all components will be inkjet printed eventually.
 

Thread Starter

daanmicro

Joined Nov 15, 2017
50
Very nice, thanks a lot!

Now my incoming signal goes from -1.46 V to 1.08 V. I don't see if this conversion will still work for a signal like this one?

Also i got another question about the capacitor in the bottom on the right, what is its function and can the system work without it? I don't know yet if it's possible to use capacitors.

Thanks in advance.
 

Bordodynov

Joined May 20, 2015
2,838
If you put a more specific task, you would get a better answer. Which transistors are you going to use (and used) for a ring oscillator? Why such strange signal levels? What is the load of the meander shaper?
 

Thread Starter

daanmicro

Joined Nov 15, 2017
50
Yeah you're right, sorry.

I'm developing a ring oscillator for an RFID tag. Because we haven't completely developed the transistors that eventually will be used (thin film transistors), i want to characterize all possible parameters and how they influence the clocking signal. Right now im just experimenting with a breadboard to improve my knowledge about transistors and ring oscillators. By the way im an engineering physics student, so im not very well known with electronics. Im using this transistor right now: https://www.infineon.com/dgdl/Infin...N.pdf?fileId=5546d462533600a4015356640fff25c5

I gotta say i sort of underestimated the whole ring oscillator, and my insights in the working principles aren't very well. I've put 7 pmos inverters (PMOSFET and 10K resistor in series) in series. This gave me the oscillation as in the image above. Now i'm trying to work towards a square wave.

Hopefully this made more clear to you about my project.
 

Thread Starter

daanmicro

Joined Nov 15, 2017
50
UPDATE

I've put my incoming signal upload_2017-12-7_16-2-55.png into spice. Now i tried another approach to convert it to a square wave. I wanted to develop a common source amplifier, which would directly 'switch' back and forth from 0 to Vdd.

Today I achieved to develop the following: (to be honest i'm not completely sure if i even made a common source amplifier the right way)

upload_2017-12-7_16-5-51.png

Well my question for now is, is this circuitry right? And besides that, how do i get the signal to be exactly periodical? I'm assuming it isn't right now.

Thanks in advance, would really appreciate some help!

Daan
 

DickCappels

Joined Aug 21, 2008
7,273
What is probably the best way to get it "exactly periodical", if I understand your meaning, is to divide it by two with an appropriate flip-flop.
 

Thread Starter

daanmicro

Joined Nov 15, 2017
50
Well what i mean is that the duration of the on and off-state are identical? assuming this is normal for a square wave?
 
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