diode v-i curves

millwood

As promised, here are the v-i curves for some RF diodes (1n5711 / e3po special request, bat54, bat85s, and sd101c).



A few observations:

1) they have substantially lower Vfwd than silicon diodes. at 50ua If or lower, Vfwd for the RF diodes is generally around 200mv, vs. 450 - 500mv for silicon diodes.
2) BAT85 beats out everyone hands down: wow! I did get them for low Vfwd but I never realized they would be this low, especially vs. 1n5711 / sd101.
3) SD101 - what a disappointment. I got it after some research for its low Vfwd. totally not worth it.
4) 1n5711 - quite frankly, I don't see what's in it (other than lower prices and better availability).
5) BAT54: not bad. especially considering that I got a reel (3000 pieces) of it for free.

I think if you are building a crystal radio, you should seriously look into BAT85/54.

I have some hsms and 1n60p somewhere but will publish their v-i curves when I find them.

I will try some highspeed schottky diodes' v-i curves tomorrow. Those are for rectification purposes, however.

millwood

i may have found the archille's hill for bat54/bat85: the capacitance. being 200ma diodes, their Ct is rated 10pf max. the Ct-Vr curve for those diodes is pretty steep for Vr < 5v.

most germanium diodes in comparison have Ct of 1pf max.

so bat54/85 could still be used for low level am detection (crystal radio). it may not be efficient for sw / fm detection.

millwood

to complete the picture, here are the v-i curves for some ultrafast silicon / schoottky diodes.



Those diodes are not meant for use as detectors - they are tested here just for fun.

mur120 / 220 are widely used in high-end audio preamps or even cd players / transport.

mbr / 1n5819 are schoottky diodes. 1n5819 is specifically designed for its low Vfwd drop, and it shows here. for If < 50ua, Vfwd < 100mv for 1n5819.

All those diodes have significant Ct. 1n5819 for example has Ct from 10pf - 100pf+, making an ideal diode for use as a variable capacitor in a voltage tuned am/sw radio.

e3po

millwood 发表于 2012-9-29 15:45
As promised, here are the v-i curves for some RF diodes (1n5711 / e3po special request, bat54, bat85 ...

      Thanks!


      fyi:
           HSMS diodes are tiny and pricy.

炉魔

老勐 发表于 2012-9-24 17:02
楼主很热心地给咱们测试了一些半导体PN结的正向伏安特性。有常见的1N4148，也有三极管的PN结，还有几种发 ...

我理解错了，我看到老国哥的贴，以为他说楼主当年没好好读书，所以如今搞不明白二极管的特性。

millwood

I tested three more diodes, 1n34a (germanium), 1n270 (germanium) and 1n60p (schottky).



the v-i curves for the new diodes are highlighted.

My take on this:

1) at anything less than 100ua, the germanium diodes performed considerably better than even the rf schottky. they start to conduct at very low voltages (the germanium diodes actually could never to shut off);
2) the germanium diodes don't perform as well as the silicon or schottky diodes at anything approaching 1 - 2ma.

So if you use your diodes as detectors for small signals, germanium diodes are the way to go. Otherwise, stay with schottky. I think bat85 and bat54 are pretty good choices 1n60p isn't too good, given its higher prices and worse availability.

ace919

相当好的一手资料！

e3po

       where/how can we find the SPICE models for all these diodes ?

      




        

眉间尺

也许最好的方法就是实测然后提取参数.

好好爱

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