But if i supply both of them with the proper voltage and run them in parallel why wouldn't it work? sorry for the questions, but i still need to learn
Also can you tell me whats an appropriate driver for the 445nm, and if possible, do you have the schematics on the on i can build? thanks alot..
As principle, you can use the schematic i have in my album, this is a sink driver, but basically sink and source current drivers share the same principle of work ..... also, mine was made for lab use, but the basical schematic of low powered drivers is almost the same:
The power element (mosfet) regulate the voltage, and the sense resistor (RSense, here is the 0.1 ohm one), is used for get a voltage (call it Vsense) from the current in the load (being in serie with the load, the current is the same in the load and in the RSense, and as you probably know, a certain current flowing in a resistor cause a certain voltage at its sides, where V=R*I, basical ohm law) ..... the voltage at the sides of RSense is controlled from an operational amplifier, that compare it with a fixed and known reference voltage (call it Vref, and varying the Vref you change the output current too), and drive the mosfet in the way that Vref and Vsense are always the same ..... when current of the load decrease, Vsense decrease, so the op-amp drive the mosfet to give more voltage to the load, til the current is again the wanted one, and the same happens (in reverse) when the current increase .....
About the voltage input, yes, the driver have a minimum total dropout (basically the drop on the Rsense plus the drop on the mosfet ..... much less than the dropout of linear regulators like LM317, but still present), so if your LD have a FV of, say, 4.5V, you must use at least 5V, better if 6V, for power up the circuit ..... but at the same time, remember that in linear drivers, ALL the power not used from the load, become dissipated in heat, mainly from the mosfet ..... so, if for the same example you use 6V for your LD, and power it with 1A, the dissipated power from the mosfet is 1.4W (6V, minus 4.5V from the LD, minus 100mV from the RSense, multiplied for the current) ..... where instead if you use 12V, the circuit still work, but the mosfet need to dissipate 7.4W ..... and so on .....
Also, more the mosfet is high current made and last technology, less is its internal RdsON (the resistance of the device when it's in ON state) , and also this contribute to the power dissipation, less is the RdsON, more efficent is the mosfet, and less total dropout, and so the whole circuit (some HexFETs can reach 8 or 10 milliohm of RdsON, where old types, low current mosfets can have 300 or 400 milliohm or more)
