Hi All,
As far as I can tell the current Onsem/Fairchild datasheet for this device does not list a maximum base current. Does anyone have an idea of what it might be?
For comparison, the max base current for the BD139/140 is 0.5A and max collector current is 1.5A (33%). Using 33% on the KSC3503's 100mA max Ic rating I would suspect 33mA is a reasonable guess.
Any thoughts?
Many thanks,
Greg
As far as I can tell the current Onsem/Fairchild datasheet for this device does not list a maximum base current. Does anyone have an idea of what it might be?
For comparison, the max base current for the BD139/140 is 0.5A and max collector current is 1.5A (33%). Using 33% on the KSC3503's 100mA max Ic rating I would suspect 33mA is a reasonable guess.
Any thoughts?
Many thanks,
Greg
Well there's never any need for the base current to exceed 10% of the collector current in normal circuits anyway, as that's hard saturation.
Yes true, but I want to know what to limit the current to under "fault" conditions in this particular circuit.
The preceding stage may overdrive it when clipping or if current limiters are activated. Base current will then be many times what it is in the linear region. Especially if the VAS is designed to go be able to go into class B to increase slew rate. That feature would require significant drive current available, and if it gets dumped into the base it needs to be able to handle it.
Exactly, thank you wg_ski. I was hoping to avoid going into the basics of transistor operating points 101 for what initially seemed to be a simple enough question.
This is why I would like to know what I should safely limit the base current to for this particular device. All current limiting implementations I have come up with for the circuit in question have some impact on performance depending on when they begin working.
It's a delicate balance between setting them as high as possible and not damaging the transistor.
Not to worry, I will conservatively assume 10 mA and be done with it.
This is why I would like to know what I should safely limit the base current to for this particular device. All current limiting implementations I have come up with for the circuit in question have some impact on performance depending on when they begin working.
It's a delicate balance between setting them as high as possible and not damaging the transistor.
Not to worry, I will conservatively assume 10 mA and be done with it.
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