The designation linear amplifier merely states that it is an amplifier whose output signal is proportional to the input signal and which can deliver power to a load.
The designation linear amplifier does not indicate whether it is an RF power ampl ifier or a power amplifier, nothing about the amplifier class or for which frequency range the linear amplifier is designed. Accordingly, there are many ways of using the term linear amplifier for the above-mentioned amplifier types. Mostly the term linear amplifier is used for power amplifiers.
These can be audio amplifiers, but also RF or microwave power amplifiers. Such an amplifier can be built with integrated circuits, but also with transistors, electron tubes or klystrons.
Logarithmic amplifiers, in contrast to linear amplifiers, are amplifiers whose gain follows a logarithmic characteristic.