I have heard from certain people on different forums that a 'base to emitter' resistor is required for 'stability' of a BJT being used as a switch. And I have heard you do not need it as well. This example I found shows it with no base/emitter resistor:
Here switch on is simple. With switch off we have open base. We can source current into Rb but in this case we do not sink Rb to ground. I know that in this situation the turn off time will be a considerably longer with no base-emitter bias resistor due to base to collector capacitance will drive the base until charged. I have used this circuit configuration multiple times with no issues. But some EE's state it can cause 'issues'. Being that the base is open when the transistor is in cutoff, this is a high impedance situation the might be susceptible to capacitive noise coupling?
Here is what many people say is the 'correct' way to build the circuit. I will admit if you require fast turn off times this is fine, but if you do not require fast turn off time, what is the benefit?
I am interested in how the community in general feels about this. I have never had issues with the no base to emitter resistor circuit.
The change is shown in red but according to many websites I have looked at that is not necessarily required:
https://www.electronicshub.org/transistor-as-a-switch/
Looking for the communities opinion on this matter. And if Rbe is required a logical reason why besides the fact that it significantly improves the turn off time. I am also very much aware that Rbe can be used to increase the 'turn on voltage' of the transistor being that it creates a voltage divider. So I know about that benefit as well.
Thanks
Here switch on is simple. With switch off we have open base. We can source current into Rb but in this case we do not sink Rb to ground. I know that in this situation the turn off time will be a considerably longer with no base-emitter bias resistor due to base to collector capacitance will drive the base until charged. I have used this circuit configuration multiple times with no issues. But some EE's state it can cause 'issues'. Being that the base is open when the transistor is in cutoff, this is a high impedance situation the might be susceptible to capacitive noise coupling?
Here is what many people say is the 'correct' way to build the circuit. I will admit if you require fast turn off times this is fine, but if you do not require fast turn off time, what is the benefit?
I am interested in how the community in general feels about this. I have never had issues with the no base to emitter resistor circuit.
The change is shown in red but according to many websites I have looked at that is not necessarily required:
https://www.electronicshub.org/transistor-as-a-switch/
Looking for the communities opinion on this matter. And if Rbe is required a logical reason why besides the fact that it significantly improves the turn off time. I am also very much aware that Rbe can be used to increase the 'turn on voltage' of the transistor being that it creates a voltage divider. So I know about that benefit as well.
Thanks