Classification of amplifiers according

Voltage amplifier: it is the amplified where only the signal voltage is amplified i.e. input and outputs are in terms of voltage only.
Current amplifier: it is an amplifier where only signal currents are amplified. I.e. input and output are in terms of current, quantities For current amplifiers, the input impedance is very large.
Trans-conduction amplifier: in this type of amplifier input voltage signals are amplified and converted into a large current signal.
Trans –resistance amplifier: in this type of amplifier input their signals are amplified and then converted into voltage signals at the output.
Power amplifier: in this type of amplifier current, as well as voltage signals, are amplifier so that sufficient amount of power signal is available across output terminal which drives the load.