noob current amplification question

[N00I3]

Hello.

I want to power a laser pointer from a uC, a simple ON/OFF mechanism. But the output-PIN can only output or sink 20mA, while the laser requires 100mA. They both run on 5VDC.

My questions:
1: What do I do? I guess I can use a transistor (or maybe an op-amp?).

2: How will I design the circuit? Do I need any resistors or caps in between the components?

3: If you could suggest a transistor (or op-amp) that would suit my needs that would be perfect (SMD components are preferable). Or maybe just point out what values I should look for in the datasheet.

I really appreciate any help Thank you!

 

[dougy83]

>> 1: What do I do? I guess I can use a transistor (or maybe an op-amp?).
Transistor would be easier

>> 2: How will I design the circuit? Do I need any resistors or caps in between the components?
Assuming an NPN transistor: Put a resistor (470R should be OK) in series with the base. Connect the emitter to ground. Connect the collector to the negative of the laser pointer. Connect the 5V supply to the positive of the laser pointer.

>> 3: If you could suggest a transistor (or op-amp) that would suit my needs that would be perfect (SMD components are preferable). Or maybe just point out what values I should look for in the datasheet.
BC817 - NPN, 45V, 500mA

Hope that helps.

 

[N00I3]

Thank you so much dougy83! Saved me a lot of boring reading time there

 

[dougy83]

No worries.

You could just have a look at the pictures on e.g. Transistor Switches or **broken link removed**