LME49830 question

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This is LME49830 diagram from appliction note.

I wonder why in every schematic, comprising appliction notes ones and also members proposals, we never see any resistor between N out and P out.

Meaning the driver stage inside the chip sees only the mosfet gates as load.

Should'nt it be beneficial to load this driver stage with some resistor as it can be seen in many mosfets amplifier schematics.

Edit: sorry i should have posted in the chipamp section.
 

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The resistor is optional; in the reference design from AN-1850, it is provided for but not installed. In a "normal" amplifier, the current flowing through that resistor biases the output stage. LME49830 has a different biasing mechanism, so the resistor (or rather Vbe multiplier) is connected to BIAS+ and BIAS- pins. There is no benefit in loading the driver stage AFAIK.
 
Yes, when Vas is directly connected to output mosfets.
Though, when a driver stage is implemented, there is usually a resistor (some hundreds ohms) between drivers emmiters. (Same position as the speed up resistor in a BJT darlington.)
In our case, drivers are inside the chip and bias circuit is in front of them.

NB:I must say i am not very familiar with mosfets.
 
Looking more deeply at the chip topology, which is unconventionnal, i do understand how it works now. The driver stage is made of two independent N and P bridged outputs. That way it becomes unnessecary for a quiescent current to run between them; so no resistor is needed.
In a conventional driver stage a resistor is needed as quiescent current cannot pass through mosfets gates.
 
:confused: I am wrong as per datasheet voltage swing is almost the same as 49810-nearly the rails-
I still asking myself what this chip has special compared to 49810.
Looks like 49810 is able to drive mosfets as well.
Why did they built two different chips?
LME49830 has a higher DC bias range for the output stage (Nout - Pout) of 16 volts so that it can drive MOSFETS, whereas LME4910 is only designed to drive BJTs in darlington (about 3 volts).
 
Did you find these LME49810 values by measurements/trials ?
Comparing datasheets they don’t look so different. (which btw isn’t so easy as not given the same way)

Lme49810
Bias Adjust Function Current : 2.8 mA
VBA Bias P&M Pin (Open Voltage BiasP – BiasM) : 10 V

LME49830
I AB Bias Control Current Shorted output, shorted bias control 2mA (1.6 mA (min) / 2.7 mA (max))
VBIAS Bias Voltage 16V
 
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Yourself say 49810 is ok for driving mosfets. (Read on your site which i already knew.)
8v should be enough which is less than 10.

I have built several bjt amps based on 49810 and also recently one based on 49830 feeding 2sk 1530/2sj201. I must say they sound identically.(not woth to spend that money on Toshibas)
I am posting in the hope of learning more about these chips.

I liked the article about audio myths.
 
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