It's cheap, it's N, it's dirty, it's.... The CIRCLOMOS!!! - diyAudio
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Old 3rd November 2009, 01:01 PM   #1
Elvee is online now Elvee  Belgium
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Default It's cheap, it's N, it's dirty, it's.... The CIRCLOMOS!!!

Not especially intended for audio applications, but could easily be adapted.
Crude, but effective (34Vpp out @ +/-20V supplies).
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Old 7th November 2009, 08:25 PM   #2
Elvee is online now Elvee  Belgium
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Default And now, it's rebaptised: it's....

....The CIRCLOFLOP!!!

However, it does have some unusual features: it is capable of directly driving unwieldy loads, such as high Q, undamped parallel or series resonant circuits, as well as pure reactive loads, at high power and high frequencies.

Look Mum, no Zobel...!....!.:
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Old 14th November 2009, 08:34 PM   #3
Elvee is online now Elvee  Belgium
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Default The Circloflop isn't dead yet...

....just on life support.

Here are some more pics:

First the simulated response to a 100KHz square wave, on a pure capacitive 100nF load.

Second, the same, but in the real world (capacitor is Siemens polypropylene B32650, 0.1/400V)

Last edited by Elvee; 14th November 2009 at 08:41 PM.
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Old 15th November 2009, 12:43 PM   #4
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Their simulations are without the capacitor coupling (C1).
What the function of R11? not missing this one capacitor!
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Old 15th November 2009, 03:45 PM   #5
Elvee is online now Elvee  Belgium
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C1 is in circuit, and it is the main compensation capacitor (not coupling).
R11 is the output load; its value varies (from 1ohm to 10 megohm) according to the type of test performed.
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Old 16th November 2009, 09:02 AM   #6
godfrey is offline godfrey  South Africa
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OK, I'll bite - what's it for then, if "not intended for audio"?

Is it running in class A or B? - I haven't simmed it but the circuit looks like it could do either. Presumably something somewhere is adjustable to set the bias?

Nice to see something different / original
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Old 16th November 2009, 09:46 AM   #7
Elvee is online now Elvee  Belgium
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Quote:
Originally Posted by godfrey View Post
OK, I'll bite - what's it for then, if "not intended for audio"?
It is a "lab workhorse", an all-purpose power amplifier, designed to drive all sorts of transducers (including loudspeakers), transformer, coils, etc, at various frequencies, from DC to ultrasonic. It also does stress-testing of components or subassemblies, to simulate load-dumping conditions f.e., or inject interferferences into power supply lines.
This is why it has to be extremely stable, robust and tolerant, without any network in the output which might degrade the accuracy.
And it has to cheap, in case things go really wrong.



Quote:
Is it running in class A or B? - I haven't simmed it but the circuit looks like it could do either. Presumably something somewhere is adjustable to set the bias?
It operates in AB, under near-square law conditions (insofar as the transfer function of the FETs permits). The Iq is about 120mA, with a strong negative coefficient (in the sim at least: with real components, heatsinks and non-ideal thermal couplings, things are more even).
The bias could be made adjustable by making part of R12 variable, but I used no trimmers, and selected D2 instead.
D5 compensates for Q3 Q5 Q6, and D6 for the output transistors.

Quote:
Nice to see something different / original
Thanks for the appreciation
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Old 21st November 2009, 08:12 AM   #8
Elvee is online now Elvee  Belgium
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Default Some further details:

First, more stress-tests.


On a (quasi) pure inductive load of 10H:
Click the image to open in full size.


The load dumping condition: the load forces an 80Vpp, 100KHz square wave (magenta) into the output of the amplifier (green). That's twice the supply voltage of the amplifier:
Click the image to open in full size.



Now, a low impedance test, with a 1ohm load (for obvious reasons, the voltage is limited to 9Vpp):
Click the image to open in full size.



Next, the load is a high-Q parallel resonant circuit:
Click the image to open in full size.



Here is a real-life application of the above simulation: inductive heating of a screw. First, the test set-up:
Click the image to open in full size.



And then the thing in action:
Click the image to open in full size.
(Sorry for the pic quality, the coil was beginning to catch fire)



A close-up of the prototype, showing the heading of the thread is properly chosen:
Click the image to open in full size.



Finally, a more serious note: a look at the distortion:
Click the image to open in full size.
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Old 21st November 2009, 09:29 AM   #9
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Quote:
inductive heating of a screw
This is the first time I see an audio amplifier doing that. At what frequency/amplitude is it?
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Old 21st November 2009, 09:57 AM   #10
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In the case of the screw, the frequency was ~45KHz, and maximum amplitude (35Vpp).
The series resonant circuit exciting the fluorescent tube was driven at around 120KHz, also 35Vpp.
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