I was tinkering around in Multisim, & came up with these designs. Nothing special in the specs department but to me, they have some curious properties of which i'm trying to establish.
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Circuit A with global feedback
Load = 1 Ohm
Input = 0.775mV RMS @ 1kHz
Distortion @ 1kHz = 0.021%
Output = 548 mV RMS  Power = 302mW

Load = 10 Ohm
Input = 0.775mV RMS @ 1kHz
Distortion @ 1kHz = 0.018%
Output = 548 mV RMS  Power = 30.2mW

Load = 100 Ohm
Input = 0.775mV RMS @ 1kHz
Distortion @ 1kHz = 0.018%
Output = 548 mV RMS  Power = 3.2mW
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Usually i would expect to see the output voltage rise proportionately with output resistance. This doesn't happen with this circuit, it stays constant, why is that ?
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Circuit B no global feedback
Load = 1 Ohm
Input = 80V RMS @ 1kHz
Distortion @ 1kHz = 2.4%
Output = 8V RMS  Power = 176W
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Load = 10 Ohm
Input = 80V RMS @ 1kHz
Distortion @ 1kHz = 1.7%
Output = 8.32V RMS  Power = 19.33W
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Load = 100 Ohm
Input = 80V RMS @ 1kHz
Distortion @ 1kHz = 1.79%
Output = 8.36V RMS  Power = 1.95W
*
I wasn't expecting to be able to drive the OpAmps at such a very high level I just kept upping the Volts to see where the distortion jumped right up. I did rise as i presumed it would, but nowhere near what i thought it might ? I managed to get it up to 100V before clipping was visable !
Why are the OpAmps "seemingly" able to take so much drive level ?
Can you see Any room for improvement in either of these designs, and where/how ?
TIA
*
Circuit A with global feedback
Load = 1 Ohm
Input = 0.775mV RMS @ 1kHz
Distortion @ 1kHz = 0.021%
Output = 548 mV RMS  Power = 302mW

Load = 10 Ohm
Input = 0.775mV RMS @ 1kHz
Distortion @ 1kHz = 0.018%
Output = 548 mV RMS  Power = 30.2mW

Load = 100 Ohm
Input = 0.775mV RMS @ 1kHz
Distortion @ 1kHz = 0.018%
Output = 548 mV RMS  Power = 3.2mW
*
Usually i would expect to see the output voltage rise proportionately with output resistance. This doesn't happen with this circuit, it stays constant, why is that ?
*
Circuit B no global feedback
Load = 1 Ohm
Input = 80V RMS @ 1kHz
Distortion @ 1kHz = 2.4%
Output = 8V RMS  Power = 176W
*
Load = 10 Ohm
Input = 80V RMS @ 1kHz
Distortion @ 1kHz = 1.7%
Output = 8.32V RMS  Power = 19.33W
*
Load = 100 Ohm
Input = 80V RMS @ 1kHz
Distortion @ 1kHz = 1.79%
Output = 8.36V RMS  Power = 1.95W
*
I wasn't expecting to be able to drive the OpAmps at such a very high level I just kept upping the Volts to see where the distortion jumped right up. I did rise as i presumed it would, but nowhere near what i thought it might ? I managed to get it up to 100V before clipping was visable !
Why are the OpAmps "seemingly" able to take so much drive level ?
Can you see Any room for improvement in either of these designs, and where/how ?
TIA