Question:
I have two identicle amplifiers. I want to take a signal and "chop it in half"; that is to say that I want all of the positive part of the signal to go to one amplifier, and all of the negative part of the signal to go to the other amplifier. Their outputs will be summed up to drive a simple speaker.
My idea here is to design an output stage using all NPN or N-channel devices for better device matching without using the quasi-complementary approach. I know that tube amps use phase splitters or transformers with center taps, but I'm trying to get a completely DC coupled amp from first to last stage.
I'm in a brain lock as to how to design such a device...
I have two identicle amplifiers. I want to take a signal and "chop it in half"; that is to say that I want all of the positive part of the signal to go to one amplifier, and all of the negative part of the signal to go to the other amplifier. Their outputs will be summed up to drive a simple speaker.
My idea here is to design an output stage using all NPN or N-channel devices for better device matching without using the quasi-complementary approach. I know that tube amps use phase splitters or transformers with center taps, but I'm trying to get a completely DC coupled amp from first to last stage.
I'm in a brain lock as to how to design such a device...
Well I (and a few others I believe) don't understand why you'd want to do this????
A diode will clip any positive or negative singal above .6V if placed correctly... but I don't think you'd want to use that aproche.
P.S. I think all your going to do is make the worst cross-over distorstion amp ever, but if you really are bored prove me wrong.
oh, good luck keeping you wave semectrical across two amps.
A diode will clip any positive or negative singal above .6V if placed correctly... but I don't think you'd want to use that aproche.
P.S. I think all your going to do is make the worst cross-over distorstion amp ever, but if you really are bored prove me wrong.
oh, good luck keeping you wave semectrical across two amps.
Perhaps you might read Douglas Self's words. I believe he understands distortions produced in amps, particularly along the lines of your concerns, very well indeed. He might put your concerns to rest.
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm
If not, Nelson Pass has written about a cascode power stage which I guess you may find interesting.
http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm
If not, Nelson Pass has written about a cascode power stage which I guess you may find interesting.
Hi Lumanauw,
Well I personnally like this kind of lateral thinking...too many ideas around here are deep inside "the box".
The perennial problem is developing a bidirectional current with uni-directional devices. The tube fraternity have solved this a million times over, so why not borrow some of their ideas?
Single-ended always works well but is wasteful of power. Circlotron has come up with some natty ways to minimize wasted power by using inductors as current sources.
If you want push-pull and don't want a transformer I know no satisfactory method that avoids p channel devices.
That doesn't mean you can't invent one! 
Well I personnally like this kind of lateral thinking...too many ideas around here are deep inside "the box".
The perennial problem is developing a bidirectional current with uni-directional devices. The tube fraternity have solved this a million times over, so why not borrow some of their ideas?
Single-ended always works well but is wasteful of power. Circlotron has come up with some natty ways to minimize wasted power by using inductors as current sources.
If you want push-pull and don't want a transformer I know no satisfactory method that avoids p channel devices.
That doesn't mean you can't invent one! 
Such a design has been published in WW years ago, I think by Sandman. Used current driven diodes (to overcome the 0.6V threshold) to route the pos polarity to the pos half of the amp, and vice versa. I'll see if i can find it.
Anyway, you would still need two complete amps. The amp that is NOT amplifying the signal still has to sink the speaker current ...
Jan Didden
Anyway, you would still need two complete amps. The amp that is NOT amplifying the signal still has to sink the speaker current ...
Jan Didden
Wireless World, 'New Approach to Class B Amplifier Design'. by Peter Blomley, Feb 1971 P.57-61
Anybody got it?
... found it:
http://www.diyaudio.com/forums/attachment.php?s=&postid=596847&stamp=1110777721
The two transistor TR4 and TR5 in the driver act as diode switches, routing the signal depending on polarity either to the pos half or to the neg half. There is no bias for the power stage, it is pure class B. The "diodes" are so fast and the gain is so high that there is (presumably) a seemless restitution of the signal at the output.
Jan Didden
Anybody got it?
... found it:
http://www.diyaudio.com/forums/attachment.php?s=&postid=596847&stamp=1110777721
The two transistor TR4 and TR5 in the driver act as diode switches, routing the signal depending on polarity either to the pos half or to the neg half. There is no bias for the power stage, it is pure class B. The "diodes" are so fast and the gain is so high that there is (presumably) a seemless restitution of the signal at the output.
Jan Didden
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