Radio Frequency

                                                                    Transistors:

All FETs can be called UNIPOLAR devices because the charge carriers that carry the current through the device are all of the same type i.e. either holes or electrons, but not both. This distinguishes FETs from the bipolar devices in which both holes and electrons are responsible for current flow in any one device.

                                                             

                                                                      AMPLIFIERS :

Amplifiers do not have the same gain at all frequencies. 

For example, an amplifier designed for audio frequency amplification will amplify signals with a frequency of less than about 20kHz but will not amplify signals having higher frequencies.