# Return to Answer

 2 indentation and grammar, and additional minor things to get to 6 characters… (sigh) edit approved Jan 7 '16 at 8:45 poke 13511 gold badge11 silver badge99 bronze badges Yes Yes. You can calculate the resistor by calculating base required current (you will need to know 'hfe' of your transistor). But you can just try. Working range is quite high, so if you will just use 500 Ohm for example, it should just work. For example, if max total current is 100mA, voltage is 5V, and hfe is 150mA, you need 100mA / 150mA = 0.6mA base current, so resistor should be 5V / 0.0006 = 8.3kOhm or less. There are lots of differences, but yes, it depends on how much current you will need in the worst case. If these LEDs are usual 10mA ones, almost any BJT will work so you can take what's cheaper or what you already have. For example, if max total current is 100mA, voltage is 5V, and hfe is 150, you need 100/150 = 0.6mA base current, so resistor should be 5V/0.0006 = 8.3kOhm or less. There are lots of difference, but yes, it's depend on how much current you will need in the worst case. If these LED's are usual 10mA ones, almost any BJT will work so you can take what's cheaper or what you already have. BTW. Don't see your shift register :-) Yes Yes. You can calculate the resistor by calculating base required current (you will need to know 'hfe' of your transistor). But you can just try. Working range is quite high, so if you will just use 500 Ohm for example, it should just work. For example, if max total current is 100mA, voltage is 5V, and hfe is 150, you need 100/150 = 0.6mA base current, so resistor should be 5V/0.0006 = 8.3kOhm or less. There are lots of difference, but yes, it's depend on how much current you will need in the worst case. If these LED's are usual 10mA ones, almost any BJT will work so you can take what's cheaper or what you already have. BTW. Don't see your shift register :-) Yes Yes. You can calculate the resistor by calculating base required current (you will need to know 'hfe' of your transistor). But you can just try. Working range is quite high, so if you will just use 500 Ohm for example, it should just work. For example, if max total current is 100mA, voltage is 5V, and hfe is 150mA, you need 100mA / 150mA = 0.6mA base current, so resistor should be 5V / 0.0006 = 8.3kOhm or less. There are lots of differences, but yes, it depends on how much current you will need in the worst case. If these LEDs are usual 10mA ones, almost any BJT will work so you can take what's cheaper or what you already have. BTW. Don't see your shift register :-) 1 answered Mar 12 '11 at 0:38 BarsMonster 1,30344 gold badges3232 silver badges7070 bronze badges Yes Yes. You can calculate the resistor by calculating base required current (you will need to know 'hfe' of your transistor). But you can just try. Working range is quite high, so if you will just use 500 Ohm for example, it should just work. For example, if max total current is 100mA, voltage is 5V, and hfe is 150, you need 100/150 = 0.6mA base current, so resistor should be 5V/0.0006 = 8.3kOhm or less. There are lots of difference, but yes, it's depend on how much current you will need in the worst case. If these LED's are usual 10mA ones, almost any BJT will work so you can take what's cheaper or what you already have. BTW. Don't see your shift register :-)