question about laser driver

[jkaiser3000]

Well, the only TO220 things I have at the moment are the tip50 and some voltage regulators (7805, lm317 and such). I will try the tip50 when I get a chance and see what happens, it's a NPN transistor like the 3904. So, one more question for now, how should I connect it?, what's the equivalent for EBC to DSG? My guess is that E=D, B=S and C=G

where:

E: emitter,
B: base,
C: collector,
D: drain,
S: source,
G: gate

[jkaiser3000]

I just found a IRFZ20 chip that is quite close to the one used originally (IRLR3105) so I will use that instead.

There is, however, one question I forgot to ask before, will everything remain the same regarding the volts to ma reading? (1mv=1ma on the MON pads)

[ajcleary]

Hi jkaiser,

I bet the TIP50 would work pretty good, but I'm guessing the IRFZ20 would be even better!

For future reference the Bipoler-to-MOSFET equivalents are

Bipolar_____MOSFET
Emitter (E) = Source (S)
Collector (C) = Drain (D)
Base (B) = Gate (G)

Always check the datasheet for which pin is which.... a lot of the TO220 devices go BCE (or GDS) from left to right when looking at the front, but not always!

As long as you use a 1 ohm resistor as shown, then 1mv=1ma. That's the beauty of a 1 ohm resistor... since V=I*R and R = 1, then the voltage across the resistor will equal the current through the resistor (V=I).

-Andy C.