Triodes

High-power triodes High-power triodes generally use a filament which serves as the cathode (a directly heated cathode) because the emission coating on indirectly heated cathodes is destroyed by the higher ion bombardment in power tubes.

Low power triodes Low power triodes have a concentric construction (see drawing right), with the grid and plate as circular or oval cylinders surrounding the cathode.

Using this technique, a small number of triodes could be made to do the work that formerly required dozens of triodes.

A typical example, the 6AG11, contained two triodes and two diodes.

A VLSI integrated-circuit die History During the mid-1920s, several inventors attempted devices that were intended to control current in solid-state diodes and convert them into triodes.

Beam power tubes can be connected as triodes for improved audio tonal quality but in triode mode deliver significantly reduced power output.

Devices with three elements are triodes used for amplification and switching.

Due to the low gain of early triodes it required 9 tubes, with 5 IF amplification stages, and used an IF of around 50 kHz.

However, at that time, no practical "short wave" (defined then as any frequency above 500 kHz) amplifier existed, due to the limitations of existing triodes.

It used 6 triodes: a mixer, local oscillator, two IF and two audio amplifier stages, with an IF of 45 kHz.

Large water-cooled triodes may be used as the final amplifier in radio transmitters, with ratings of thousands of watts.

Of particular interest is the 17-minute video showing the manual production of triodes.

The Audion was incompletely evacuated and ionization of residual gas in it caused it to function somewhat differently from the later thermionic "hard vacuum" triodes.

These types were the first true hard vacuum tubes; early diodes and triodes performed as such despite a rather high residual gas pressure.

The terms "amplifier" and "amplification" (from the Latin amplificare, 'to enlarge or expand' citation ) were first used for this new capability around 1915 when triodes became widespread.

Triodes are used for amplifiers and oscillators.

Triodes were widely used in consumer electronics devices such as radios and televisions until the 1970s, when transistors replaced them.