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In electronics, cathode bias (also known as self-bias, or automatic bias) is a technique used with vacuum tubes to make the direct current (dc) cathode voltage positive in relation to the negative side of the plate voltage supply by an amount equal to the magnitude of the desired grid bias voltage.
Combinations of bias methods may be used on the same tube. Fixed bias: The DC grid potential is determined by connection of the grid to an appropriate impedance that will pass DC from an appropriate voltage source. [2] [4] Cathode bias (self-bias, automatic bias) - The voltage drop across a resistor in series with the cathode is utilized. The ...
Plate detector circuit with cathode bias. Cathode bias RC time constant three times period of lowest carrier frequency. C L is typically around 250 pF.. In electronics, a plate detector (anode bend detector, grid bias detector) is a vacuum tube circuit in which an amplifying tube having a control grid is operated in a non-linear region of its grid voltage versus plate current transfer ...
[40] [41] For certain directly heated cathode tubes, the optimum grid bias is at a positive voltage relative to the negative end of the cathode. For these tubes, a dc path is provided from the grid leak to the positive side of the cathode or the positive side of the "A" battery; providing a positive fixed bias voltage at the grid determined by ...
It was introduced in the summer of 1955 with a rated power output of 15 watts, cathode bias, two 6V6 output tubes, and a 5Y3 tube rectifier. The Tremolux was the first Fender amp with a built in effect, tremolo. [1] In 1957, the rated power output of the Tremolux was increased to 18 watts when it changed to a fixed bias design and a 5U4 rectifier.
The Wehnelt is biased to a negative voltage (typically −200V to −300V) relative to the emitter, which is usually a tungsten filament or Lanthanum hexaboride (LaB 6) hot cathode with a V-shaped (or otherwise pointed) tip. This bias voltage creates a repulsive electrostatic field that suppresses emission of electrons from most areas of the ...
Directly heated cathode: In this type, the filament itself is the cathode and emits the electrons directly. Directly heated cathodes were used in the first vacuum tubes, but today they are only used in fluorescent tubes , some large transmitting vacuum tubes, and all X-ray tubes.
The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, tetrode and pentode, used to control the flow of electrons from the cathode to the anode (plate) electrode. The control grid usually consists of a cylindrical screen or helix of fine wire surrounding the cathode, and is surrounded in turn by ...