Matching at idle current

[diy didi]

Hi.
I have a question. Why do many folks suggest matching at the amplifier's quiescent current. Doesn't the amount of current through parallel connected transistors vary with a load and signal?
Or am I understanding this the wrong way. Does matching at quiescent current, ensure linear, equal sharing throughout, regardless of load and signal level??

[AndrewT]

look at the Vbe vs Ic of a BJT.

Now look at a parallel pair of output BJTs.
For simplicity assume the base currents are the same.
What is the Vbe difference between the two output devices?

If one output device is selected randomly from the box and when connected up, it passes 1A of quiescent current and the other BJT passes 500mA of quiescent current from the same Vbe, then consider the operating temperature Tj of the two BJTs? Which one runs hotter?

Go back and look at the temperature effect on the Vbe vs Ic graph. Will the warmed up devices still be passing 500mA and 1000mA.

[diy didi]

Thanx Andrew!
Point well made!