output impedance of source follower and load in mH?

AudioGeek · 17th November 2005, 09:07 PM

If i wanted to load a pair of push pull source followers with a transformer similar to the susan parker design... how do i determine what primary inductance is needed and with a particular output impedance of the source followers what should the load on the secondary of the transformers be?

Is there a good website that explains this?

what is output impedance of a source follower mathematically?

thanks!

theChris · 17th November 2005, 11:18 PM

1/gm for small signal analysis

gm = (2 S Kpn Ids/n)^0.5 if memory serves at least.

but those specs probably aren't available. not sure how to mathmatically get them. maybe test it out with a common gate amplifier.

of course this doesn't count feedback which can lower output impedance.

EWorkshop1708 · 18th November 2005, 11:02 PM

I wonder if you could use a toroid trans, but drive the CT secondary with the push pull, and either wind your other side yourself, for speaker impedance, or use the 120V primary to get a HV output to get either really loud speakers, or use on 70V line trans.

17th November 2005, 09:07 PM	#1
AudioGeek diyAudio Member Join Date: Jan 2004 Location: Minnesota	output impedance of source follower and load in mH? If i wanted to load a pair of push pull source followers with a transformer similar to the susan parker design... how do i determine what primary inductance is needed and with a particular output impedance of the source followers what should the load on the secondary of the transformers be? Is there a good website that explains this? what is output impedance of a source follower mathematically? thanks! __________________ It is not you... you are it.

17th November 2005, 11:18 PM	#2
theChris diyAudio Member Join Date: Dec 2001 Location: SIUE, Illinois, USA	1/gm for small signal analysis gm = (2 S Kpn Ids/n)^0.5 if memory serves at least. but those specs probably aren't available. not sure how to mathmatically get them. maybe test it out with a common gate amplifier. of course this doesn't count feedback which can lower output impedance. __________________ if only it could be used for good, not evil...

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18th November 2005, 11:02 PM	#3
EWorkshop1708 diyAudio Member Join Date: Nov 2004 Location: Florida	I wonder if you could use a toroid trans, but drive the CT secondary with the push pull, and either wind your other side yourself, for speaker impedance, or use the 120V primary to get a HV output to get either really loud speakers, or use on 70V line trans.