Although both transistors and grid-controlled tubes (e.g. triode, tetrode and pentode) can render the job of amplification, they differ in the following respects:
- The electron tube is a voltage driven device while transistor is a current operated device.
- The input and output impedances of the electron tubes are generally quite large. On the other hand, input and output impedances of transistors are relatively small.
- Voltages for transistor amplifiers are much smaller than those of tube amplifiers.
- Resistances of the components of a transistor amplifier are generally smaller than the resistances of the corresponding components of the tube amplifier.
- The capacitances of the components of a transistor amplifier are usually larger than the corresponding components of the tube amplifier.