What is the advantage of triode?

Answer 1

With a diode tube you have no control over the current flow and it can only be used as a rectifier, where the triode consist of a control grid, to control the flow of electrons that will reach the anode, this make it possible to use the triode as a amplifier, compared to a transistor the control grid have the same function as the base of the transistor.

Advantages?

Over tetrodes and pentodes:

1. Operation at higher radio frequencies,

2. Lower noise figures,

3. Simpler circuitry and only one power supply.

Answer 2

Virtually all transistors are triodes. The few exceptions are the obsolete tetrode types.

Your answer?

Triode transistors are used for all applications of transistors.