Overloading an output , blows transistors why?

[danny davis]

Why does over-loading an output cause transistors to blow or have excessive current to flow through them?

Can over-loading raise the DC supply voltage? why does over-loading raise the DC supply voltage?

 

[chuckey]

You do not give a circuit or state what sort of overload you are thinking about. Most "overloads" result in excessive current in the transistor so results in over heating and its final demise after a period of time. Voltage overloads occur instantaneously, blasting a hole in the junction.
Frank

 

[danny davis]

Overload i mean a load on the output of the circuit, why does overload cause excessive current to flow through the transistors? Example if u plug to many things in your ac outlet it will overload the circuit or ac outlet causing it to catch on fire. I guess the load draws to much current but why would the transistors have excessive current flow or heat up?

 

[umery2k75]

In terms of semiconductor physics, transistor safe operating current range is given in the datasheet. If you take them further, a phenomenon known as thermal runaway will occur. It occurs due to heat up, the internal resistance starts to drop even more allowing more current to flow, before such occur. Normally such transistor are sensed by ptc/ntc to shutdown the system. Before this occurs. You can add safeties like placing safe value resistor to limit the current. place current transformer or use shunt resistor to sense it before its too late. Means you need to make smart circuit which will sense these dangers.

 

[danny davis]

But i still don't understand why overloading the outputs of a circuit or unit will cause excessive current to flow and heat up components, any reason why? Is it because the overloading is drawing to much current?

 

[chuckey]

Overloading normally means drawing too much current.
Plugging too many things into an AC outlet, in this country causes the fuse to blow because our AC systems are designed properly.
Frank

 

[danny davis]

why do components overheat and blow if the output is overloaded? the overloading is drawing to much current but why would the components before the output overheat and blow?