Quasi? Class B?

xeclipse · 10th January 2011, 02:30 PM

Hi,
I'll be straight to the point:i know what quasi comp is, is it the same thing as class B?
Regards.

Workhorse · 10th January 2011, 02:35 PM

Quote:

Originally Posted by xeclipse

Hi,
I'll be straight to the point:i know what quasi comp is, is it the same thing as class B?
Regards.

Nops, both are different things.

Class- B is mode of operation of an amplifier.

Quasi-complementary is output stage configuration where there is only one polarity of output devices are used to emulate complementary stage.

Kanwar

xeclipse · 10th January 2011, 04:01 PM

Does it imply that class B can still have complementary outputs?

Workhorse · 10th January 2011, 04:06 PM

Quote:

Originally Posted by xeclipse

Does it imply that class B can still have complementary outputs?

yes

toprepairman · 10th January 2011, 06:53 PM

Looks like a copy of Doug Self's excellent book is called for.

xeclipse · 11th January 2011, 05:43 AM

So, how do you implement class B in the driver circuit it terms of biasing?

ontoaba · 08:43 AM

Heheh.. I got it. quite difficult question. Is that you mean, to implement class B in quasi are challenging.

dunno where to place the bias.

xeclipse · 11th January 2011, 09:21 AM

Look at this:
QUASI Amplifier for Beginners
works with one to five pairs with no bias adjustment!

ontoaba · 11th January 2011, 09:59 PM

No.. That amplifier outputs is biased with two 1n4148 diodes. the driver stage working at class AB and output stages working in near class B. Adds more pair makes both working in class AB (more idle bias;pure Class B have not consuming any idle current)
I am also using 10 ohm Rbe for TIP41/42 outputs to make them work in class B , and let the driver working in class AB. There is appear 100R in quasibeginner, that you may change them into 10ohms and re adjust the bias to be smaller to prevent driver in over current.

10th January 2011, 02:30 PM	#1
xeclipse diyAudio Member Join Date: May 2010 Location: Where the world's best tea come from:Kericho Kenya	Quasi? Class B? Hi, I'll be straight to the point:i know what quasi comp is, is it the same thing as class B? Regards. __________________ if there are no sparks,it probably doesn't work!

10th January 2011, 04:01 PM	#3
xeclipse diyAudio Member Join Date: May 2010 Location: Where the world's best tea come from:Kericho Kenya	Does it imply that class B can still have complementary outputs? __________________ if there are no sparks,it probably doesn't work!

11th January 2011, 05:43 AM	#6
xeclipse diyAudio Member Join Date: May 2010 Location: Where the world's best tea come from:Kericho Kenya	So, how do you implement class B in the driver circuit it terms of biasing? __________________ if there are no sparks,it probably doesn't work!

11th January 2011, 08:35 AM	#7
ontoaba diyAudio Member Join Date: Nov 2009 Location: Kudus, & Malang	Heheh.. I got it. quite difficult question. Is that you mean, to implement class B in quasi are challenging. dunno where to place the bias. Last edited by ontoaba; 11th January 2011 at 08:43 AM.

11th January 2011, 09:21 AM	#8
xeclipse diyAudio Member Join Date: May 2010 Location: Where the world's best tea come from:Kericho Kenya	Look at this: QUASI Amplifier for Beginners works with one to five pairs with no bias adjustment! __________________ if there are no sparks,it probably doesn't work!


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10th January 2011, 06:53 PM	#5
toprepairman diyAudio Member Join Date: Nov 2010	Looks like a copy of Doug Self's excellent book is called for.

11th January 2011, 09:59 PM	#9
ontoaba diyAudio Member Join Date: Nov 2009 Location: Kudus, & Malang	No.. That amplifier outputs is biased with two 1n4148 diodes. the driver stage working at class AB and output stages working in near class B. Adds more pair makes both working in class AB (more idle bias;pure Class B have not consuming any idle current) I am also using 10 ohm Rbe for TIP41/42 outputs to make them work in class B , and let the driver working in class AB. There is appear 100R in quasibeginner, that you may change them into 10ohms and re adjust the bias to be smaller to prevent driver in over current.

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