Tweakers' Asylum

RE: Why do they have a diode and cap symbol on them?

63.26.40.163

Solder n Listen

In Reply to: RE: Why do they have a diode and cap symbol on them? posted by Tweekeng on May 10, 2009 at 12:50:47

That is the symbol for a varactor diode. Varactor is derived from "variable reactance"; the capacitance of this diode changes with applied voltage.
This is a sort of voltage-controlled capacitor, used in RF tuning circuits
and oscillators, since the capacitance is in the pf range.

As to why they used this symbol............, perhaps they meant to imply that there are parasitic effects present in diodes that they have circumvented; that's only a guess. I haven't heard these fuses myself.

Follow Ups:

Thanks for the correction - Solder n Listen 17:42:40 05/13/09 (0)
It's been a few decades since I've seen these in a circuit.

And maybe I should make sure I'm actually awake before I post....

Thanks.
VARAC DIODE symbol - budm 12:49:44 05/11/09 (0)
http://www.electronics-radio.com/articles/electronic_components/diode/varactor-varicap-diode.php
- http://www.electronics-radio.com/articles/electronic_compone (Open in New Window)
That is the symbol for a varactor diode.? - Tweekeng 06:24:22 05/11/09 (3)
This is a variactor diode.

That is a diode with a capacitor bypassing it.
- wrong symbol for a cap - jimmyjames 12:30:33 05/12/09 (2)
  that symbol is an open contact in the control world.
  
  "E pur si muove...And yet it moves"
  - It's both - Tweekeng 14:21:01 05/12/09 (1)
    Oh my, I didn't think anyone else here ever dabbled in Relay Ladder Logic.
    They are not still using RLL for PLC's are they? I would hope they moved on to something a little more powerful like LabView.
    But you are correct that symbol is a normally open relay contact in RLL and a nonpolerized capacitor in schematics.
    
    Edits: 05/12/09 05/12/09 05/12/09
    - Big Electrons - jimmyjames 06:50:30 05/13/09 (0)
      in the world of power distribution and control, or the world of "big electrons" as one of my coworkers used to say, power contacts and even little bitty control relay contacts are shown like that symbol in schematics and catalog literature.
      
      "E pur si muove...And yet it moves"

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