| 词条 | Cut-off (electronics) |
| 释义 |
In electronics, cut-off is a state of negligible conduction that is a property of several types of electronic components when a control parameter (that usually is a well-defined voltage or electric current, but could also be an incident light intensity or a magnetic field), is lowered or increased past a value (the conduction threshold). The transition from normal conduction to cut-off can be more or less sharp, depending on the type of device considered, and also the speed of this transition varies considerably. Cutoff valuesDiodes
Transistors
{{anchor|Tubes}}Valves
Remote cutoffA vacuum tube (such as a pentode, but also sometimes triodes, hexodes, heptodes and so on) with its control grid given a helix with a variable pitch can be made to operate with more negative grid voltages, with reduced amplification, before it is completely cut off (i.e. yielding no significant output). This ability to vary the amplification (sometimes called mu) and also the transconductance, is useful in Automatic Gain Control (AGC) stages of radio receivers. Devices with this characteristic are called remote-cutoff or variable-mu or super-control types. Sharp cutoffWith a normal control grid arrangement, a vacuum tube will have close to a square-law relationship between input (grid) voltage and output (anode/plate) current, with the latter falling sharply to roughly zero. This characteristic is normally required for linear RF and audio uses. Examples; EF86 and 6AK5. Semi-remote cutoffA semi-remote cutoff device has characteristics somewhere between a remote-cutoff device and a sharp-cutoff one. ReferencesSee also
External links
1 : Electrical parameters |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。