Talk:Zener diode

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Contents

[edit] Schematic Symbol

Isn't the schematic symbol in the top right photo for a Schottky diode? I always thought the Zener symbol had the tips at a 45 degree angle.

Hyperlight 00:40, 13 April 2007 (UTC)

A Schottky diode has extra bits on the tips. See Diode for a list of symbols. I have seen zener's shown with angled tips (eg in Bill Orr's "Radio Handbook") but more of the references I have (eg ARRL Handbook, Silicon Chip) use the image shown here. images.google.com also shows a variant with only one side of the cathode bar having a bent tip. I know there are standards but I don't have references to them. --PeterJeremy 09:18, 15 May 2007 (UTC)

In Australia, at any rate, the symbol for a Zener diode is the same as that shown except that the top does not have the right angle tip. Source is Standards Associoation of Australia 1986, SAA Hb3 - Electrical and Electronic Drawing Practice for Students. I believe this is also the standard symbol in the UK. Perhaps there should be a picture of the two (or three) standard forms of drawing the Zener diode symbol along with the region to which they apply. —Preceding unsigned comment added by 124.171.252.31 (talk) 07:16, 7 September 2007 (UTC)

The Schottky should have a "hat" that looks more like a fancy "S" (for Shottky). The Zener should have a hat that looks like a "Z". The "Z" not only stands for Zener, but it looks like the i-v curve. So, the symbol on the page as is now should be flipped (so it looks like a Z). --TedPavlic | talk 00:09, 23 April 2008 (UTC)

[edit] Diode destruction

IIs the reason that a normal diode "destroys itself" due to avalanche breakdown? If so, then we should say this explicitly. Also, a diode doesn't ever really destroy itself, unless it is connected to a very low resistance path. In this case, a diode can destroy itself in reverse bias as well as forward bias, can it not? So, we should remove this vagueness I think, and be a bit more clear. I can make the changes, I just want to check with the other authors first. I guess I could also check a textbook, but I don't have one with me right at this moment. --User:Dgrant

Sort of. Avalanche breakdown in itself doesn't damage the device; in fact the effect is used a lot for small current amplification in devices like p-i-n avalanche photodiodes. What really destroys the device is the excessive current flow. If that current flow is limited by external circuitry, the diode could remain operational in its avalanche breakdown region. So yes, as you said, the diode can just as easily be destroyed at high forward bias because of excessive current. -- uberpenguin @ 2006-06-25 13:14Z

[edit] Zener breakdown

We should also have a diagram to show how Zener breakdown occurs. Without a diagram showing the mechanism and/or the I-V relationship, this article is sadly, fairly useless. I will draw one homemade using Xfig, unless someone beats me to it. --User:Dgrant

we should also have a graph showing the break down voltage and the knee voltage in the V-I relationship [user:shandhir]

[edit] pronunciation

There seems to be disagreement on whether Zener is pronounced like "zeener" or "zenner," possibly a British/American distinction. Authoritative comments on this would be helpful. --teejaydub

The Chambers Dictionary (British) says "zeener", which is annoying, because I have always pronounced it "zenner". Perhaps "zenner" is more natural for Brits because of the "zed"/"zee" thing. --Heron 20:22, 29 July 2005 (UTC)

hahahaha —Preceding unsigned comment added by 203.129.52.61 (talk) 09:37, 16 October 2007 (UTC)

[edit] unneccessary statement

"Zener diodes are widely used in electronic circuits." - when else are diodes used? I'm totally deleting that one. Fresheneesz 21:34, 2 February 2006 (UTC)

[edit] uses

I've been studying this topic, and am wondering what the effect of the resistor in the shunt voltage regulator is. Does the remaining voltage lie across it? What values are reasonable, etc? --Drewnoakes 22:38, 21 April 2006 (UTC)

[edit] Transwiki note

Most or all of this article was transwikied to wikibooks 18:37, 16 August 2006. Anyone know why? The user (IP only) did not copy the edit history or talk... I'll be happy to do that if there's a reason it was sent over. --SB_Johnny | talk 23:55, 16 August 2006 (UTC)

[edit] Zener Breakdown

More information on the Zener Diode Breakdown would be great!!

A very thin energy barrier due to large reverse bias and allowed energy states on both sides of the barrier gives rise to a high probability of quantum tunneling, a.k.a. Zener breakdown. -- mattb @ 2006-09-19T17:17Z

[edit] Behaviour at low current

"If insufficient current flows through D, then UOUT will be unregulated, and could rise as high as UIN." - could someone provide a reference for this claim. A zener diode can be modelled as a perfect zener diode with a resistor in series and a resistor in parallel. Whilst the output is unregulated at low currents (heavily dependent on the current flow through the diode), the output voltage will always be less than the nominal zener voltage. --PeterJeremy 00:50, 5 December 2006 (UTC)

In view of the lack of comments, I have corrected the statement, adding a reference to the behaviour of Voltage regulator tubes - which do behave as was previously written. --PeterJeremy 09:01, 18 December 2006 (UTC)

I believe that UOUT can in fact rise to as high as UIN. Assume as stated above that a zener diode may be modelled as an ideal zener with a resistor in series (Rs) and another in parallel (Rp). Below the zener voltage this model reduces to a resistor with value Rs+Rp. The voltage UOUT across this resistor will be UIN x (Rs+Rp)/(Rs+Rp+R) where R is the resistor in series with the zener shown in the schematic. This can be as high as UIN for (Rs+Rp) very large relative to R (the usual case).

If there are no comments I will make this change. May 6 2007

In the "usual case", the current through the diode will be in the flattish area above the knee current. To reduce the current through the diode, you need to increase R so (Rs+Rp) will never be very large relative to R. A study of the I/V curve for a zener diode will more clearly show the behaviour but I haven't been able to locate a datasheet with an I/V curve in it. Rummaging around with Google finds [1] and [2] - both of which include typical curves. --PeterJeremy 09:29, 15 May 2007 (UTC)

Rs ≪ R ≪ Rp if you haven't abused your diode. —Ryan 09:23, 9 November 2007 (UTC)

[edit] Is this the same as a "thyrector"?

I once saw a thing called a "thyrector" in an old 60's era schematic. I remember it being drawn as ->|<- so I imagine it as being two Zener diodes connected in opposite directions, which would provide A/C voltage regulation. Is this correct? This would make it different from, say, a "diac" which would avalanche above the break voltage. —Preceding unsigned comment added by 66.68.159.105 (talk) 00:47, 10 April 2008 (UTC)