A novel harmonic oscillator circuit

[Winterstone]

Hello,

with this thread I like to inform you that I have placed a new article under the heading "theory" proposing a new harmonic oscillator circuit - based on the GIC principle.

The article was written as a WORD file and translated into pdf format.
Because I was not succesful to copy and paste the complete pdf document it appears only as an attachement. But I hope it can be opened.

Comments are welcome.

To the administrator: If this should be not the correct way of publishing I kindly ask you to take some correcting actions or to give me some advice how to modify the presentation.

Thank you.

wintersone

Link added.
https://www.electro-tech-online.com/threads/balun-wire-lenght.546/

 

[cowboybob]

I would like to see it.

 

[ericgibbs]

hi W,
You had not 'checked' the Publish option, done it for you.

I would suggest you place a link on your first post, to the Article.

Moderation. E

EDIT:
hi W.
I see you have now removed the PDF.????
Eric

 

[Winterstone]

Hi Eric,

thank you.
In the meantime I have revised the pdf due to a small error. It is again available

W.

 

[ericgibbs]

Hi Eric,

thank you.
In the meantime I have revised the pdf due to a small error. It is again available

W.

Have sent you a PM with brief guidance details
E.

 

[Winterstone]

I would like to see it.

It's available now - see post#1.

 

[cowboybob]

Thanks, I see it. Very interesting.

 

[The Electrician]

In the article you say "It is well known that the first part of Zin,2 can represent a grounded inductance (Z3 or Z5 capacitive) or a frequency dependent negative resistor (FDNR) with two capacitive numerator elements. While both alternatives can be used for oscillator applications only the preferred method based on inductor simulation is described in the following."

Why is the inductor simulation method preferred? In what sense is it preferred? If you could show that this oscillator topology had some advantage, such as, perhaps, reduced sensitivity to opamp parasitics, or passive component variations, the article's value would be increased.

 

[ccurtis]

Why is the inductor simulation method preferred? In what sense is it preferred?

Practitioners in the art widely understand that good (high Q), passive inductors at low (audio) frequencies are harder to achieve relative to good quality, passive capacitors, and they tend to be relatively large and expensive.

Edit: But hey, it never hurts to make something clear where there might be some question.

 

[The Electrician]

Your comment is not relevant to what I am asking Winterstone. The question is not whether a high Q simulated inductor is easier (cheaper?) to achieve than a high Q passive inductor at audio frequencies. The question is why a simulated inductor method is preferred compared to the FDNR method.

 

[ccurtis]

Your comment is not relevant to what I am asking Winterstone. The question is not whether a high Q simulated inductor is easier (cheaper?) to achieve than a high Q passive inductor at audio frequencies. The question is why a simulated inductor method is preferred compared to the FDNR method.

My apologies. I now see that I was careless!

 

[The Electrician]

De nada.

I hope Winterstone will have more to say. The GIC is an interesting circuit and there doesn't seem to be much interest in analog these days, so I hope some further discussion ensues.

 

[Winterstone]

Hi Electrician,
Yes, I agree that my remark concerning the "preferred" solution needs some explanation.

To be honest – I must confess that I have some problems to justify my claim that the inductance-type would have advantages.
More than that – as mentioned in the article – the same circuit can be regarded as an FDNR-type oscillator if seen from the right side of the drawing.
I agree that, indeed, this makes my statement questionable.
In fact, presently I prefer the „inductance“-version for two reasons:

1.) It is more easy to explain (I know, it’s not a good reason). From my experienc with many students I have learned that it is not so easy to understand the principle
of R-FDNR resonance (in contrast to the well-known L-C resonance effect). Thus, the principle of the circuit is easier to describe and to understand in case of L-C resonance.
Otherwise, one would have to realize that an R-FDNR tank circuit can be undamped using a negative capacitance!

2.) The problem is that – under ideal conditions – the performance of all active filters/oscillator topologies is the same. Distinction become evident only under real conditions (tolerances, parasitics).
And my simulations have revealed that the signal quality of one FDNR type (Z2 and Z4 capacitive) is not as good as the other versions (for real amplifier models).
However, this should be considered as a preliminary statement only because calculation of the THD in the simulator is not very exact.
More than that, in the C2-C4 case no capacitor is grounded which may be a slight disadvantage.

In summary, all versions have quite similar properties, but some might be easier to understand than others.

Finally, I have a good example to illustrate my foregoing explanations:
When I realize an FDNR-type oscillator using Z2=1/sC2 and Z6=R6 + 1/sC6 (R6 is necessary for balancing Rx) I arrive exactly at the inductor-type topology
as shown in the article (due to symmetry properties of the circuit).

Thank you for your interest.
W.

 

[MrAl]

Hi there Winterstone,


I was wondering the same thing about the true advantages, but it is still kind of interesting nonetheless.

Im not sure how 'involved' i want to get with this circuit but i can add a little more information for this particular circuit...

First, the exact expression for the frequency is given by:
w=sqrt(4*R2*R6-(Rx-R1)^2)/(2*C*R2*R6)

and you'll note the presence of R1 and Rx in this expression, and that's because they have a slight influence (although it will be small in most cases). You might also want to note that if Rx=R1 the expression dissolves into your expression for frequency:
f=1/(2*pi*C*sqrt(R2*R6))
However R1 can not be allowed to equal Rx. And the relationship between R1 and Rx brings us to the next item.

It looks like the exponential part of the response requires that Rx be greater than R1. If this is not upheld, then we end up with a damped exponential and of course that wont get us anywhere near the operation required for an oscillator. We need an increasing exponential where we take control of the damping via some forced means (such as diodes or clipping). This also means the equation for Q can be modified to remove the absolute value signs and reverse Rx and R1.

Also, to investigate component variation on the frequency we can use this equation which does not impose any restrictions on any of the values:
w=sqrt(4*C1*C5*R2*R3*R4*R6-C1^2*R2^2*Rx^2+2*C1^2*R1*R2*R3*Rx-C1^2*R1^2*R3^2)/(2*C1*C5*R2*R4*R6)
where
w=2*pi*f



I hope this information helps a little but as i said im not sure how involved i want to get with this circuit although it is interesting.

I do also have a question:
What parasitics are you most interested in, op amp internal gain and/or others?

 

[Roff]

I haven't read this.
**broken link removed**

 

[Winterstone]

I haven't read this.
**broken link removed**

No surprise for me - since I was the author of this design idea. The article available in this forum is a revised version. In particular, the Q expression was not correct in the referenced paper.
Thanks.
W.

 

[Winterstone]

Hi there Winterstone,

Im not sure how 'involved' i want to get with this circuit but i can add a little more information for this particular circuit...

Hi again, MrAl.

Thank you for your reply and those "little more information".
I suppose it will take some time for me to go through your calculation and formulas (at present I am involved with more private things).
But I will come back to your post at a later time.
Regards
W.

 

[Roff]

No surprise for me - since I was the author of this design idea. The article available in this forum is a revised version. In particular, the Q expression was not correct in the referenced paper.
Thanks.
W.

I suspected that was the case.
I am surprised that the original article apparently escaped the notice of hobbyists. A sine wave oscillator which can be tuned by a single resistor is obviously very desirable.

 

[Roff]

An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. They are widely used in many electronic devices.

Thanks for informing us..

What post are you responding to?


EDIT: Never mind. After reading some of your other posts, I think I know what you're about.

 

[MrAl]

Hi again, MrAl.

Thank you for your reply and those "little more information".
I suppose it will take some time for me to go through your calculation and formulas (at present I am involved with more private things).
But I will come back to your post at a later time.
Regards
W.

Hi,

You're welcome. I know what you mean about the private matters too as i've had a number of those time consuming events in my life too as of late. I hope i have as much interest when you get back to this though

In the mean time, perhaps you can point out some of those parasitics that i asked about. What is of most concern to you.

BTW the circuit i was responding to was the one in the .pdf file that was available yesterday 07/17/2012 not the one in the more recent link posted which i think is a little outdated. I've included an attachment of the circuit so there is no mistake about which circuit i was looking at.