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Old 25th February 2012, 04:40 PM   #1
Elvee is offline Elvee  Belgium
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Default Just for fun: UcD on a shoestring

Here is a truly minimalist amplifier: a total of 4 transistors, and it actually works, it has been built.

I think it would be difficult to make even simpler without seriously compromising something.

Click the image to open in full size.

Have fun!!!
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Old 25th February 2012, 05:53 PM   #2
Eva is offline Eva  Spain
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Brilliant. This renders all other previous ZEN work (and thinking) obsolete.

btw: I think you mislabeled IRF9530 as IRFP530.
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Old 25th February 2012, 06:12 PM   #3
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by Eva View Post
btw: I think you mislabeled IRF9530 as IRFP530.
Sorry about that: as there was no IRF9530 in the native library, I simply changed the sex of a IRF530 as a quick fix.
The transistor I used in my prototype was in fact a IRF9630, and I forgot to edit the name after the sim was completed.
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Old 25th February 2012, 06:16 PM   #4
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I know you did this for fun, but how well does it work?

This is simple enough for even me to build; not that I understand how it functions in the least. Have the parts to do it though, so why not.
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Old 25th February 2012, 07:10 PM   #5
luka is offline luka  Slovenia
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I got to say, this one will be hard not to just try and see, just for the fun of it
did you try it on any other voltages too, I got few supply, that have a bit higher voltage
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Old 25th February 2012, 08:01 PM   #6
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by theAnonymous1 View Post
I know you did this for fun, but how well does it work?
Difficult to tell: other than a dummy load, I tested it on an unboxed 4" speaker.
In those conditions, it sounded normal....


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did you try it on any other voltages too, I got few supply, that have a bit higher voltage
No I didn't. I tested it on a regulated supply, and with unregulated supplies there would probably be ripple rejection issues.
It could probably tolerate somewhat higher supplies, but at some point, the gate voltage might become excessive, as this is not controlled in any way.
Up to +/-20V should be safe, but be careful...
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Old 25th February 2012, 08:04 PM   #7
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Very cool!
Question: how do you change the sex of an IRF530?
(I mean in LTspice)
-E
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Old 25th February 2012, 08:31 PM   #8
stewin is offline stewin  Kenya
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nice one elvee. do the outputs heat at 2 ohms playing hard?
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Old 25th February 2012, 08:52 PM   #9
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by elevator View Post
Very cool!
Question: how do you change the sex of an IRF530?
(I mean in LTspice)
-E
Want to try on yourself? Naughty boy!
Open the standard.mos library with a text editor, copy and paste the line of the victim transistor, and edit "nchan" into "pchan", and also edit the component name in recognizable way; when I do this kind of "operation", I add a P or a N somewhere, and I take care not to duplicate any real component.
When it's done, it looks like this:
Quote:
.model IRFP530 VDMOS(pchan Rg=3 Vto=-4 Rd=50m Rs=12m Rb=60m Kp=5 lambda=.01 Cgdmax=1n Cgdmin=.26n Cgs=.2n Cjo=.4n Is=52p mfg=International_Rectifier Vds=100 Ron=160m Qg=26n)
which is an ideal complement for the IRF530.
Not very realistic in real life, at least for MOS transistors. For BJT's, it is less of an issue, you can find real components that are almost an ideal match.

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nice one elvee. do the outputs heat at 2 ohms playing hard?
I tried only on 8Ω, full power (12V supplies) and the transistors remained cool.
Only the 18µH coil was hot, but it was an ordinary iron powder (white yellow) toroid, not quite suited to the ~200KHz switching frequency
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Old 25th February 2012, 09:30 PM   #10
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Quote:
Originally Posted by Elvee View Post
Want to try on yourself? Naughty boy!
Actually I've already tried the sim with other complementary pairs, and it works nicely. So I just wanted to reproduce your original.
Thanks much for the directions, cheers
-E
Edit: I believe the P version should also have Vds changed to -100
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Last edited by elevator; 25th February 2012 at 09:43 PM.
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