Still waiting for a Tutorial On......

Genomerics · 4th August 2006, 04:29 PM

Quote:

Does anyone of the formula for the oscillating frequencies and gain for this amp? Thanks in advance.

DNA

BWRX · 4th August 2006, 08:58 PM

Maybe if you were a little more specific or included some sort of reference as to what that statement refers to someone could help.

poobah · 4th August 2006, 09:08 PM

How can the first post in a thread have a quote?

BWRX · 4th August 2006, 09:23 PM

I would blindly guess that the gain is approximately equal to the feeback resistor divided by the input resistor

poobah · 4th August 2006, 09:30 PM

Yep... and that resistor must have silver leads!

And they should be Kobe resistors from Japan. These are special resistors massaged daily and fed beer.

fokker · 4th August 2006, 09:51 PM

I asked that question in the thread on UcD / LtSpice.

Conceptually, it is the ratio between the resistor / cap network and the base resistor (1K in the case of the original UcD).

so you would think increasing the upper resistor would increase the gain. It does, but only to an extent as the impedance of the resistor / cap side comes dominant and at that point increasing the resistor doesn't help.

In other words, the maximum gain is capped by the resistor / cap network.

Increasing that will change the behavior of the feedback system and may cause the oscillation to stop.

The oscillation frequency is determined by the output filter. a filter with high cornor frequency will cause the amp to oscillate faster.

Somehow, I hope someone will come out with a set of formula that will tie the two together.

analogspiceman · 4th August 2006, 10:05 PM

Quote:

Originally posted by Genomerics

DNA

analogspiceman · 4th August 2006, 10:15 PM

PS: that was meant to be humorous.  I always enjoy your comments and provocative point of view. -- a.s.

BWRX · 4th August 2006, 11:23 PM

The equations to figure out the gain and the oscillating frequency can be found here.

poobah · 4th August 2006, 11:31 PM

and here

4th August 2006, 08:58 PM	#2
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	Maybe if you were a little more specific or included some sort of reference as to what that statement refers to someone could help. __________________ Brian

4th August 2006, 09:23 PM	#4
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	I would blindly guess that the gain is approximately equal to the feeback resistor divided by the input resistor __________________ Brian

4th August 2006, 11:23 PM	#9
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	The equations to figure out the gain and the oscillating frequency can be found here. __________________ Brian

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4th August 2006, 09:08 PM	#3
poobah diyAudio Member Join Date: Nov 2005	How can the first post in a thread have a quote?

4th August 2006, 09:30 PM	#5
poobah diyAudio Member Join Date: Nov 2005	Yep... and that resistor must have silver leads! And they should be Kobe resistors from Japan. These are special resistors massaged daily and fed beer.

4th August 2006, 09:51 PM	#6
fokker diyAudio Member Join Date: Jul 2006	I asked that question in the thread on UcD / LtSpice. Conceptually, it is the ratio between the resistor / cap network and the base resistor (1K in the case of the original UcD). so you would think increasing the upper resistor would increase the gain. It does, but only to an extent as the impedance of the resistor / cap side comes dominant and at that point increasing the resistor doesn't help. In other words, the maximum gain is capped by the resistor / cap network. Increasing that will change the behavior of the feedback system and may cause the oscillation to stop. The oscillation frequency is determined by the output filter. a filter with high cornor frequency will cause the amp to oscillate faster. Somehow, I hope someone will come out with a set of formula that will tie the two together.

4th August 2006, 10:15 PM	#8
analogspiceman diyAudio Member Join Date: Sep 2004 Location: Yahoo, USA	PS: that was meant to be humorous.  I always enjoy your comments and provocative point of view. -- a.s.

4th August 2006, 11:31 PM	#10
poobah diyAudio Member Join Date: Nov 2005	and here

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