Dependent source

[1] Practical circuit elements have properties such as finite power capacity, voltage, current, or frequency limits that mean an ideal source is only an approximate model.

Accurate modeling of practical devices requires using several idealized elements in combination.

A voltage controlled by a current has a proportionality factor expressed in units of resistance (ohms), and this constant is sometimes called "transresistance".

A current controlled by a voltage has units of conductance (siemens), and is called "transconductance".

Transconductance is a commonly used specification for measuring the performance of field effect transistors and vacuum tubes.

A simple electric circuit made up of a voltage source and a resistor. Here, , according to Ohm's Law .