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TIP125 base resistor

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venkates2218

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1.Is R9 is required here..?
2.Need to add any resistor to emitter circuit.png on TIP125..?
 

1. Yes, or the current through the B-E junctions will almost certainly damage one or both transistors.
2. depends on how much current has to flow through the load but probably no.

Brian.
 
circuit.png
In O/P side in going to connect 12v/1A lamp(Filament and LED lamp)..Is freewheeling is required here..?
If it is required means this circuit is correct..?
 

The 'freewheeling' diode is only needed when the load is inductive. An inductor produces a voltage back into the circuit when the current through it is turned off and that is what the diode protects against. A filament lamp or LED do not produce a voltage back so the diode isn't needed.

Otherwise the circuit is correct. The load will turn off if the input voltage is +12V and it will turn on when it is lower than about +11.4V.

Just be careful if the load is ONLY an LED as they do not inherently limit their own current, a series resistor would be required. A filament lamp regulates it's own current as it's resistance increases with temperature.

Brian.
 
The 'freewheeling' diode is only needed when the load is inductive. An inductor produces a voltage back into the circuit when the current through it is turned off and that is what the diode protects against. A filament lamp or LED do not produce a voltage back so the diode isn't needed.

Otherwise the circuit is correct. The load will turn off if the input voltage is +12V and it will turn on when it is lower than about +11.4V.

Just be careful if the load is ONLY an LED as they do not inherently limit their own current, a series resistor would be required. A filament lamp regulates it's own current as it's resistance increases with temperature.

Brian.
The load will turn off if the input voltage is +12V and it will turn on when it is lower than about +11.4V.

I can't this line....sorry...Please explain this line...
 

Hi

In post#1 you show that your control signal is 5V level.

In post#3 you don't show this. This circuit will work with 12V/0V levels only. It doesn't work with 5V levels.

Klaus
 
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