Bored in LTspice on a friday afternoon

Tekko · 21st January 2011, 12:55 PM

I was a bit bored so i whipped this together:

http://i.imgur.com/3nkXQ.jpg

I dunno about you but to me it looks pretty much like symasym, this circuit simulates about 0.04% THD at 120W and 20kHz so its not a very good one, and with no capacitor on the input and feedback it probably wouldent work if i decided to build it, which i don't have enough transistors to do anyways.

But as i said, its the result of boredom and i thought i just wanned to share.

Don't complain on my choice of output and driver transistors plz

there are not a whole lot to choose from in LTspice.

alexcp · 21st January 2011, 02:10 PM

When you put current mirrors on both sides of a complementary input stage, the quiescent current of the VAS depends on transistors' betas, which are not reliable. It is not a problem in a simulation, when all transistors are identical. In reality, you either have to use more complicated current mirrors or to be satisfied with simple resistors there.

jaycee · 21st January 2011, 03:52 PM

Tekko, LTSpice will use any standard SPICE models. If you want, you can also edit lib/cmp/standard.bjt and add them there. I prefer to just .include or .lib them

Tekko · 21st January 2011, 03:58 PM

I had no intention of actually building this thing.

21st January 2011, 12:55 PM	#1
Tekko diyAudio Member Join Date: Jan 2005	Bored in LTspice on a friday afternoon I was a bit bored so i whipped this together: http://i.imgur.com/3nkXQ.jpg I dunno about you but to me it looks pretty much like symasym, this circuit simulates about 0.04% THD at 120W and 20kHz so its not a very good one, and with no capacitor on the input and feedback it probably wouldent work if i decided to build it, which i don't have enough transistors to do anyways. But as i said, its the result of boredom and i thought i just wanned to share. Don't complain on my choice of output and driver transistors plz there are not a whole lot to choose from in LTspice.

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21st January 2011, 02:10 PM	#2
alexcp diyAudio Member Join Date: Jun 2009 Location: Florida Blog Entries: 28	When you put current mirrors on both sides of a complementary input stage, the quiescent current of the VAS depends on transistors' betas, which are not reliable. It is not a problem in a simulation, when all transistors are identical. In reality, you either have to use more complicated current mirrors or to be satisfied with simple resistors there.

21st January 2011, 03:52 PM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	Tekko, LTSpice will use any standard SPICE models. If you want, you can also edit lib/cmp/standard.bjt and add them there. I prefer to just .include or .lib them

21st January 2011, 03:58 PM	#4
Tekko diyAudio Member Join Date: Jan 2005	I had no intention of actually building this thing.

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