page_title: Triode
section_title: Characteristics
hierarchical_section_title: Triode / Characteristics
caption_attribution_description: English: Voltage-current characteristic of triode ECC83. Data from ECC83 Phillips datasheet was used. Српски / srpski: Приказана је напонско-струјна карактеристика триоде ECC83. Кориштени су подаци произвођача фирме Phillips. Русский: Семейство анодных характеристик вакуумного триода ECC83 производства Phillips.
context_page_description: A triode is an electronic amplifying vacuum tube consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate. Developed from Lee De Forest's 1906 Audion, a partial vacuum tube that added a grid electrode to the thermionic diode, the triode was the first practical electronic amplifier and the ancestor of other types of vacuum tubes such as the tetrode and pentode. Its invention founded the electronics age, making possible amplified radio technology and long-distance telephony. Triodes were widely used in consumer electronics devices such as radios and televisions until the 1970s, when transistors replaced them. Today, their main remaining use is in high-power RF amplifiers in radio transmitters and industrial RF heating devices. In recent years there has been a resurgence in demand for low power triodes due to renewed interest in tube-type audio systems by audiophiles who prefer the sound of tube-based electronics.
  The name "triode" was coined by British physicist William Eccles sometime around 1920, derived from the Greek τρίοδος, tríodos, from tri- and hodós, originally meaning the place where three roads meet.
context_section_description: In triode datasheets, characteristics linking the anode current (Iₐ) to anode voltage (Vₐ) and grid voltage (Vg) are usually given. From here, a circuit designer can choose the operating point of the particular triode.
  In the example characteristic shown on the image, if an anode voltage Vₐ of 200 V and a grid voltage bias of −1 volt are selected, a plate (anode) current of 2.25 mA will be present (using the yellow curve on the graph). Changing the grid voltage will change the plate current; by suitable choice of a plate load resistor, amplification is obtained.
  In the class-A triode amplifier, an anode resistor would be connected between the anode and the positive voltage source. For example, with Rₐ = 10000 ohms, the voltage drop on it would be
  VRa = Iₐ × Rₐ = 22.5 V if an anode current of Iₐ = 2.25 mA is chosen.
  If the input voltage amplitude (at the grid) changes from −1.5 V to −0.5 V (difference of 1 V), the anode current will change from 1.2 to 3.3 mA (see image). This will change the resistor voltage drop from 12 to 33 V (a difference of 21 V).
  Since the grid voltage changes from −1.5 V to −0.5 V, and the anode resistor voltage drops from 12 to 33 V, an amplification of the signal resulted. The amplification factor is 21: output voltage amplitude divided by input voltage amplitude.
caption: ECC83 triode operating characteristic.
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