Tube Characteristics īelow is an explanation of various tube parameters:Īnode(Plate) voltage (more accurately, V ak or V pk, as it is the voltage relative to the cathode)Īnode resistance (internal.

Vacuum tubes rely on thermionic emission of electrons from hot filament. In electronics vacuum electron tube or valve is a device that controls current. If the voltage applied to the Anode becomes negative relative to the Cathode, no electrons will flow. The voltage difference in the direction from the cathode to the anode is known as the forward bias and is the normal operating mode. The anode is generally kept more positive than the cathode and so it draws the electrons off of the cathode. The electrons normally float on the surface of the cathode and this is called a space charge. The filaments are constructed of heat the cathode to about 800 degree Celsius, at which point the cathode begins to emit electrons. The filaments usually run at low voltages (6V and 12V are common, though tubes can be found with a variety of filament voltages). These are similar to the filaments one would find in a standard light bulb. This is the basis of the Vacuum Tube amplifier. By applying a negative voltage to the grid it is possible to control the flow of electrons.

NOTE: A tube with 3 elements (one grid) is a TRIODE, with 2 grids a TETRODE, with 3 grids a PENTODE.Ī Grid between the cathode and anode controls the flow of electrons. Grid(s): metal gratings or grids are placed between the Cathode and Anode to produce devices that can amplify signals. Current will flow only when the Anode has a positive voltage relative to the Cathode. The negative electrons flow from the Cathode to the Anode.Ī vacuum tube with just Cathode and Anode elements is a DIODE. Plate): Is a conductive (usually metal) plate that is connected to a positive voltage. Cathode: (electron emitter) has an electrically heated filament (which you can usually see glow red ) which spits out electrons that travel through the vacuum to the Anode (electron acceptor). Inside the tube are two or more 'Elements'. Vacuum Tube Basics Ī Vacuum Tube is a container (usually of glass) from which the air is removed. Voltage Regulator: an active component which accepts a range of voltages and outputs one constant voltage.Passive components have no gain and are not valves They are also generally preferred in guitar amplifiers both for their smoother clipping in overdrive and the warmer tone.įinally, vacuum tubes are used in high frequency communications (at frequencies that would destroy solid state components) as well as satellite and military communications due to their durability (they stand up to solar radiation better than solid state and are immune to electromagnetic pulse). Vacuum tubes are frequently used in high end Hi Fi amplifiers and are generally desirable over transistors for their 'warmer' tone. While, for most electronics, vacuum tubes have been replaced by transistors, there are still some uses for which vacuum tubes are desired. Vacuum tubes are also referred to as thermionic tubes, thermionic valves, electron tubes, valves and just plain tubes. The triode, which allowed for voltage and power amplification, was invented 3 years later in 1907 by Lee De Forest. These initial tubes could only be used for rectification. The first vacuum tube diodes were created by Thomas Edison in 1904.

Vaccuum tubes in proteus 8