Transistors acting as resistors

[mvpshaq32]

From what I understand, transistors can be viewed as several things, one of which is a resistor.

So how much resistance is a transistor turned on generally equivalent to?

And what is normally considered a large or small resistance? I know voltmeters have a large internal resistance in the order of megaohms. And I believe transistors are in the order of kilos, so would transistors acting as resistors be considered as having a low resistance?

 

[Runei]

Some bipolar transistors, when turned fully on, will have a voltage drop across the collector and emitter of approximately 0.3 volts (silicon based).

For MOSFET's, when turned fully on, there is a on-resistance in the order of milliohms. I would suggest looking at the datasheet for the transistor using.

If you are using the small-signal model of a transistor then you will be able to describe it as resistors and controlled current/voltage sources.

 

[Bobbywhy]

Certain MOSFETS are used a voltage-controlled variable resistors. Google "Siliconix VCR"