How do I calculate the inherent noise of this amplifier?

[Plecto]

I could add a resistor in series with the two diodes to adjust the bias current, but that doesn't help with the fact that the caps will block DC thus preventing the op-amp from adjusting DC offset.

 

[AndrewT]

I said the minimum was to add emitter resistor to each output device.

 

[jackinnj]

+1 for firing up TINA-TI. It's a free download from Analog, Embedded Processing, Semiconductor Company, Texas Instruments - TI.com.

~Tom

TINA Noise Analysis of the OPA454 amplifier application on their website:

 

[cbdb]

wwenze: I have a question about this way of biasing a class AB stage:

An externally hosted image should be here but it was not working when we last tested it.

If I go with global feedback on this configuration the amp won't have any DC gain so the op-amp can't change the DC output, right? It will just ram the output to either +V or -V unable to compensate for the DC offset, right? How is this solved? I find settling for local feedback unsettling 😛

The resistors set the bias current, the dc output is set by the resistors and diodes, if there matched it should be near zero. The base emitter voltage is always .6 ish volts when the transistor is on.