Understanding Diode Display on a C.R.O.

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The discussion focuses on understanding the cathode ray oscilloscope (C.R.O.) display for a diode circuit, particularly when supplied with AC input. It highlights that the output waveform will show clipping on one side, indicating the diode's conduction phase, and emphasizes that the diode requires a certain bias voltage to start conducting. Participants clarify that the displayed waveform will reflect only one half of the AC cycle due to this clipping. The conversation also touches on the forward voltage drop for different types of diodes, noting that it typically ranges around 0.6 to 1 volt. Overall, the thread provides insights into interpreting diode behavior on a C.R.O. in an AC circuit context.
QueenFisher
i have to draw the c.r.o. display for a diode, is it just the same as for an a.c. input but with the parts that were below the x-axis, intead reflected in the x-axis?
 
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I don't quite follow you.. Are you supplying AC to a diode (and hopefully a load resistor) and looking at the time varying characteristics of voltage on a scope? Or are you interested in the voltage versus current charateristics of the diode which can be measured with a curve tracer? (See second to last row for diode examples)
 
i assume that i have a circuit with a diode in it, connected to a c.r.o., and i have to draw the voltage/time shape that it would produce. e.g. for mains ac you would get a sinusoidal wave form - that's the kind of setting I'm on.
 
What is a c.r.o. ?
 
The signal will be clipped on one side, this is actually when the diode is conducting - it's resistance is low. In the attachment the zero voltage level is the dotted line.
 
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Integral said:
What is a c.r.o. ?
c.r.o. - cathode ray oscilloscope

andrevdh that's right, only one half of the cycle would be displayed, the other half is clipped. (though on yours, it appears, there was a negative dc bias applied as well).
QueenFisher, can you guess what a diode in this configuration, is also called?
 
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What I am try to indicate is that the diode needs a bit of bias (depending on the type of diode) before it starts to conduct. It does not conduct straight away.
 
andrevdh said:
What I am try to indicate is that the diode needs a bit of bias (depending on the type of diode) before it starts to conduct. It does not conduct straight away.
Why is it a negative DC bias? What are some example magnitudes for turn-on voltage of a diode (Ge, Si, PIN) ?
 
It just depends on which way round you connect the diode or the oscilloscope in the circuit. I could just as well have drawn the mirror image of the diagram. The forward voltage drop is usually of the order of 1 volt (0.6 for silicon diodes).
 
  • #10
yeah it depends really
 

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