# What's the most complicated circuit you know?

1. Jan 15, 2012

### fbs7

By that I mean a circuit that can't be broken into separate blocks that... err... do something by themselves.

For example, one can get a pretty lengthy circuit consisting of an RF amplifier / mixer / oscillator / IF amplifier / FM demodulator / audio amplifier / power amplifier / etc... but these are really individual blocks joined in together, which many times can be used for other unrelated applications (as that same power amplifier can amplify a PC audio output).

So, while a FM radio may be a complicated little thingie, it is built out of smaller blocks that, once identified, can be analyzed one by one. I'm talking about those building blocks themselves... what's the most complicated one you know of?

For that I nominate the cubic-function generator by Cipriani and Takeshian from Conexant:

Anything else can beat that?

2. Jan 15, 2012

### jim hardy

self-saturating magnetic amplifier

3. Jan 15, 2012

### Averagesupernova

Having formerly worked for a test equipment manufacturer, my list is quite long.

4. Jan 15, 2012

### fbs7

You have a sample of that circuit?

5. Jan 15, 2012

### Kholdstare

How do you determine how much complicated a circuit is ???

6. Jan 15, 2012

### jim hardy

i might have physical one laying amongst my junk, and i have two books on them

newer book is 1954 by Willaim A Geyger, "Magnetic Amplifier Circuits"

older has sumberged amid the chaos.... it was around 1940

to my considerable surprise they are making a comeback as feedback elements in switching power supplies !
to me they were the best for ultra-reliable critical low frequency applications like our emergency diesel voltage regulators. ( never trust a computer with anything important )

they still defy precise mathematical analysis because of the nonlinearity of magnetics.

here's a nostalgic writeup..

http://www.themeasuringsystemofthegods.com/magnetic%20amplifiers.pdf [Broken]

Last edited by a moderator: May 5, 2017
7. Jan 15, 2012

### Physineer

All circuits that displays chaotic behavior, at least 2-D, are really beyond deterministic modeling. They can be numerically simulated, that is all.

8. Jan 15, 2012

### fbs7

Each can use their own criteria.. this is not an exact thread - it's just curiosity :)

9. Jan 15, 2012

### fbs7

Wow, that's fascinating stuff.

I have to admit, perhaps I may have heard something about this in college, but if I did I forgot everything. I don't remember anything about "magnetic amplifiers".

Thank you, Jim.

10. Jan 15, 2012

### Kholdstare

Haha, yes.

Well I'll suggest 10 Transistor SRAM cell.

11. Jan 15, 2012

### Kholdstare

Its some wonderful stuff. But interference might be a problem here.

Last edited by a moderator: May 5, 2017
12. Jan 15, 2012

### Kholdstare

Also PTAT bandgap reference circuits.

13. Jan 15, 2012

### Physineer

I can do better.

A single bipolar transistor common emitter amplifier...with a damaged junction.

It displays mind-boggling complexity (chaos), if one tries to study the output as a function of the input.

14. Jan 15, 2012

### Bobbywhy

Old Jim, Thanks for the Mag Amp pdf document! I read it over with great memories...I adjusted the Mag Amps on the AN/APQ-72 Fire Control Radar in the F-4B Phantom. (1963) They were used in a servo-control loop of the hydraulically actuated parabolic radar antenna. They were extremely sensitive to adjust. An ordinary metal screwdriver coming near to them would affect their output. We finally learned to use wooden "orange sticks" to set them. The complexity of their theory of operation is more than I could ever digest or understand.

Last edited by a moderator: May 5, 2017
15. Jan 16, 2012

### fbs7

That's a fair point, but what's the function of a circuit that is chaotic and can't be modeled or predicted? Besides generating a chaotic and unpredictable signal, that is?

16. Jan 16, 2012

### jim hardy

fbs7 and phys -- - i think that's why life is lived forward and understood backward.

"I have never been able to think things out. I have to live them out, thinking as i go along." eric hoffer

17. Jan 16, 2012

### Kholdstare

http://www.electrical-picture.com/bandgap-voltage-reference-circuits/ [Broken]

http://www.national.com/rap/Application/0,1570,24,00.html [Broken]

Some bandgap references. Have fun "thinking".

Last edited by a moderator: May 5, 2017
18. Jan 16, 2012

### f95toli

Some circuits have "regions" in their parameter space where they are chaotic and very useful (unless you want to for example generate noise), but might exhibit predictable (using numerical methods) behaviour elsewhere.
Certain types of parametric amplifiers would presumably be an example, especially bifurcation amplifiers.

19. Jan 16, 2012

### Kholdstare

Yeah! But, does not the nonlinearity of the amplifier belong to the nonlinearity of a single device?

20. Jan 16, 2012

### Physineer

Encryption.

Pass a signal through a chaotic circuit and as long as the inverse chaotic behavior can by synthesized (like the key) the original signal can be recovered. Research has found chaotic circuits with inverses.