d123
Advanced Member level 5
Hi,
Yes, you can use the 2N4401 instead of the 2N2222, the 2N4401 is another TUN - general purpose NPN. I probably know about as much as you, my main advice with transistors is to become familiar with the datasheets and always look for the SOA graph in the datasheet to get a quick idea of what can and can't be done with it. Check minimum turn-on/turn-off base voltages required, deciding between the need for a small signal or a medium power or a high power BJT, stuff like that.
TVS is transient voltage suppressor. Zeners and TVSs/Transils aren't my forte at all, I'm afraid. Someone else would have to tell you what voltage would serve as a voltage-limiting protection device and how best to implement either. One appropriate Zener is the same as three smaller appropriate ones (except for presumably lower individual power dissipitation in the stacked diodes). You need to choose the right voltage rating at about the maximum (and minimum) current you expect the circuit to draw otherwise it won't output the expected voltage at all - as an example, I got caught out with that and chose Zeners that need 240mA to actually output their nominal 5.1V, I didn't know at the time that the required current rating is as important as the voltage and could have done with a 1mA Zener...
For TVSs, This might be interesting: TVS in Automotive Applications
A simple appropriately-sized fuse (100mA, 10A, etc.) at the positive input is a must on every circuit. If you have spare voltage and can lose 0.7V to 1.4V, a series rectifier diode after the fuse will protect against reverse polarity connection mistakes.
Yes, you can use the 2N4401 instead of the 2N2222, the 2N4401 is another TUN - general purpose NPN. I probably know about as much as you, my main advice with transistors is to become familiar with the datasheets and always look for the SOA graph in the datasheet to get a quick idea of what can and can't be done with it. Check minimum turn-on/turn-off base voltages required, deciding between the need for a small signal or a medium power or a high power BJT, stuff like that.
TVS is transient voltage suppressor. Zeners and TVSs/Transils aren't my forte at all, I'm afraid. Someone else would have to tell you what voltage would serve as a voltage-limiting protection device and how best to implement either. One appropriate Zener is the same as three smaller appropriate ones (except for presumably lower individual power dissipitation in the stacked diodes). You need to choose the right voltage rating at about the maximum (and minimum) current you expect the circuit to draw otherwise it won't output the expected voltage at all - as an example, I got caught out with that and chose Zeners that need 240mA to actually output their nominal 5.1V, I didn't know at the time that the required current rating is as important as the voltage and could have done with a 1mA Zener...
For TVSs, This might be interesting: TVS in Automotive Applications
A simple appropriately-sized fuse (100mA, 10A, etc.) at the positive input is a must on every circuit. If you have spare voltage and can lose 0.7V to 1.4V, a series rectifier diode after the fuse will protect against reverse polarity connection mistakes.