CrossRoads:
MOSFET uses voltage levels to turn on and off, very little input current, like 1microAmp. Outputs can be found with very low Rds (Resistance from drain to source) making them look very much like a mechanical switch.
Power dissipated in the device is then related to current flow, P = IIR, so for high current, low Rds is very beneficial.
1A1A.010 ohm = .01W.Bipolar Junction Transistor (BJT, NPN type and PNP type) need current into the base to let current flow from collector to emitter, with a more or less fixed voltage across C to E (Vce) of 0.5 to 0.7V.
Since Vce doesn't change, power dissipated by the device can be high. P=IV, so 1A.5ohm = 0.5W. Big difference.In this application tho, where the current flow is low, but the voltages are also low, the low Rds of the MOSFETs makes more sense to use so the voltage swings can look more like the switch contacts you are duplicating.
Witch MOSFETS do you recommend for me? May be useful for other projects as well. Want both types, N channel and P channel.