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Old 17th June 2012, 02:48 PM   #531
AndrewT is offline AndrewT  Scotland
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I did a check on the numbers being presented in the plot.
@ Vin=0.5V
Vout=6V
V*I=10W
IR7*2=1.8A, IR7 = 900mA
IR8*2=0.3A, IR7 = 150mA
Id1*4=0.16A, ID4 = 40mA
Id2=N/A

From these I can calculate that Iout = IR7*2 + Id1*4 - IR8*2 = 1.66A
Gain = Vout / Vin = 12 (this seems very high !)
Peak instantaneous Power = 6V * 1.66A = 10Wpk
Vrs = 450mV
ID4 = 40mA @ 450mVf

These (except for gain) seem to make much sense.
They indicate that when at quiescent bias, the diodes are effectively OFF.
When the output current has risen to twice the bias current, i.e. maximum ClassA output current of 1Apk, the diodes have a fairly low current contribution.
When the amplifier has transitioned into ClassAB operation the diodes begin to make a significant output current contribution.

Other than the odd gain, this is the information I have been looking for.

Can we compare a high Vrs quiescent setting and how the diode current contribute to the output current for this?

I'll be rash and make a prediction.
If Ibias requires a voltage across the diodes that turns the Diodes ON, then we will see that "kink" in the plots. Can we do a differentiation of the current slope to show up the kink more easily?
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Last edited by AndrewT; 17th June 2012 at 02:53 PM.
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Old 17th June 2012, 02:50 PM   #532
Woody1911a1 is offline Woody1911a1  United States
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Quote:
Originally Posted by AndrewT View Post

How do I reset to my normal view of windows?

ctrl + scroll back to whatever size you like
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Old 17th June 2012, 02:53 PM   #533
palmito is offline palmito  United States
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On most modern web browsers, zooming the page in/out is standardized to holding the control key and using the plus (+) and minus (-) keys to zoom in/out respectively. Holding the control key down and pressing zero (0) resets the window to its original size.

I'm not a mac person, so on the mac it may be the funky option key instead of the control key.

However, with most images on web pages, which are of a fixed size, If they are already displayed with a one to one image pixel to screen pixel resolution, zooming will just "replicate" pixels and will make the image fuzzy. The more you zoom, the fuzzier it will get.
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Old 17th June 2012, 03:06 PM   #534
buzzforb is offline buzzforb  United States
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Question. What would happen if you removed the resistors? second question. How is the use of diodes different then putting a cap across the Rs?
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Last edited by buzzforb; 17th June 2012 at 03:22 PM.
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Old 17th June 2012, 03:21 PM   #535
lhquam is offline lhquam  United States
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Quote:
Originally Posted by AndrewT View Post
I did a check on the numbers being presented in the plot.
@ Vin=0.5V
Vout=6V
V*I=10W
IR7*2=1.8A, IR7 = 900mA
IR8*2=0.3A, IR7 = 150mA
Id1*4=0.16A, ID4 = 40mA
Id2=N/A

From these I can calculate that Iout = IR7*2 + Id1*4 - IR8*2 = 1.66A
Gain = Vout / Vin = 12 (this seems very high !)
Peak instantaneous Power = 6V * 1.66A = 10Wpk
Vrs = 450mV
ID4 = 40mA @ 450mVf

These (except for gain) seem to make much sense.
They indicate that when at quiescent bias, the diodes are effectively OFF.
When the output current has risen to twice the bias current, i.e. maximum ClassA output current of 1Apk, the diodes have a fairly low current contribution.
When the amplifier has transitioned into ClassAB operation the diodes begin to make a significant output current contribution.

Other than the odd gain, this is the information I have been looking for.

Can we compare a high Vrs quiescent setting and how the diode current contribute to the output current for this?

I'll be rash and make a prediction.
If Ibias requires a voltage across the diodes that turns the Diodes ON, then we will see that "kink" in the plots. Can we do a differentiation of the current slope to show up the kink more easily?
The gain is correct. Look at Nelson's F5 Turbo V2 schematic. The feedback network has 2 x 220 ohm resistors in parallel (110 ohms) and 10 ohms to ground. That is a 12:1 divider.

I will work up a different presentation show output stage open-loop transconductance vs output current.
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Old 17th June 2012, 03:33 PM   #536
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Woody1911a1 View Post
ctrl + scroll back to whatever size you like
does not reset. Yes one can guess at what one thinks is about right.

Quote:
Originally Posted by palmito View Post
........Holding the control key down and pressing zero (0) resets the window to its original size............
this resets, whether I use the number pad or the numbers above the alpha pad.

Thanks.
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Old 17th June 2012, 03:34 PM   #537
lhquam is offline lhquam  United States
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Here is another plot. It shows the transconductance of the upper MOSFET stage and currents through the source resistors and diodes versus the input voltage.
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File Type: gif turbo-gm-sim4.gif (13.9 KB, 453 views)
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Old 17th June 2012, 03:51 PM   #538
jacco vermeulen is offline jacco vermeulen  Netherlands
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The I(D)-I(R7) envelope looks good.
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Old 17th June 2012, 03:55 PM   #539
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F5 Turbo is posted
KLUNK!-!KNULK

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Old 17th June 2012, 04:21 PM   #540
buzzforb is offline buzzforb  United States
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IlQuam,
Have you run this same simulation at higher bias through Rs?
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