Transistor type with lowest forward voltage drop?

more info would be helpful. fast switching or slow? how much current are you putting through it? analog or digital signal?

my initial thought was a MOSFET. See if you like this one. Looks like you can get about 8 A out of it before you reach 0.2V source to drain voltage, mind you I doubt your current is that high so a more reasonable estimate might be about 50 mV drop. it scales pretty linearly as long as you make sure your gate to source voltage is high enough.

voltage/power/current ratings are probably way high on this one but you get the idea

Mosfet Voltage Drop

Forward Voltage Drop

Germanium transistors have much lower forward voltage drop (0.1 volt) than silicon transistors (0.6 volt).

But they have higher collector - base leakage current, and are easily destroyed by allowing the temperature of the leads to get too hot when soldering - the leads must be heat sunk before soldering.

But you can apply a bias to a silicon transistor to nearly eliminate the forward voltage drop issue with silicon. Connect the emitter of a silicon transistor to a potentiometer or voltage divider connected to a negative bias voltage and you can adjust the base-emitter turn on threshold to anything you want.

It depends on the current. Silicon transistors connected backwards, C and E reversed, have voltage drops of as low as 5 mV, but only at very low currents.

Power MOSFETS have a strictly resistive drop, so it depends on the current. I have seen Ron as low as 0.05 ohms, which means that at 1 amp, you have a 50 mV drop.

But a lot depends on the current and on other factors. For example, for a MOSFETS, you need about 5 volts to turn the part on. If you count that as part of the voltage drop, then they probably would not be suitable.

email me with more details.

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Better yet is a heterojunction transistor. Unfortunately you'll have to pay for one in more kidneys than you have. If the base and emitter are germanium and the collector is silicon, then you have a very low forward voltage drop and an extremely high Beta value with a very very high cutoff frequency.

I assume you mean the voltage across the output when the device is conducting. In this case a MOSFET has a lower Vds than a BJT Vce.