Help understanding gain bandwidth product

[antknee]

I'm currently learning about the LM3886 audio amplifier and a non inverting board with gain of 11. The chip has a minimum GBP of 2MHz but they are rated at up to 8MHz. THe load is just a resistor of 4 ohms and i'm working in the frequency range above audio.

I understand gain bandwidth product as for example this: Gain (11) x bandwidth (100KHz) =< GBP (2MHz)

What I'm finding is the output is also voltage dependant. And it is this bit I don't understand.

For example if I drop the input voltage down to 0.1V I can go up to 500KHz.

How is GBP also voltage dependant?

I have also noticed clipping in some circumstances. The reason for that came to me at that time but has since vanished. Why does that occur?

Thanks for your help.

Antknee.

 

[crutschow]

There is another characteristic that is voltage/frequency dependent and that is the Slew-rate (typically given in V/µs). This limits the peak output voltage for a given frequency. The maximum slew-rate of a sine-wave is 2Π*f*Vp where Vp is the peak sine-wave voltage.

 

[antknee]

Yes that makes sense. Thanks!

THe slew rate is 19V/us max, 8V/us min. So at 100KHz I should get a minimum Vp= 12.7V.

25V peak to peak is quite good at that frequency.

Thanks,

Antknee.