SIGE rectifiers?

[pinkjimiphoton]

https://www.futureelectronics.com/resources/featured-products/nexperia-bipolar-transistors-and-diodes#silicongermaniumrectifiers


https://youtu.be/r2qOMuKUGqo

wondering if we couldn't use these for clipping?

[puretube]

Try one, for less than half a buck:
https://www.mouser.de/c/?marcom=180772076
also available @ digikey
e.g.:
https://www.mouser.de/datasheet/2/916/PMEG200G20ELP-2634426.pdf

[amptramp]

Is the forward voltage that different from a standard rectifier?  The typical 620 / max 700 mV is unlikely to be all that different from a 1N4148 or 1N4007.

[puretube]

Is the forward voltage that different from a standard rectifier?  The typical 620 / max 700 mV is unlikely to be all that different from a 1N4148 or 1N4007.

That`s @ >100mA
Look at Fig.3: close to 200mV @ 1mA (okay, @ 125°C ...)

Maybe it`ll bring back that nostalgic germanium-feeling temperature-instability?

[iainpunk]

Is the forward voltage that different from a standard rectifier?  The typical 620 / max 700 mV is unlikely to be all that different from a 1N4148 or 1N4007.

That`s @ >100mA
Look at Fig.3: close to 200mV @ 1mA (okay, @ 125°C ...)

Maybe it`ll bring back that nostalgic germanium-feeling temperature-instability?

they are more temp-stable than Si diodes! have a long, curvy knee and are noisy as frick if the load current is too low.
i used them in a school project where we neded low voltage drop rectification. we ended up with a 1000uF filter cap to supress the noise of the power supply, while we drew less than 150mA with our load and control circuit. i imagine using them as clipping diodes also imparts some noise.

cheers

[puretube]

Thanks!

[Ben N]

So I guess sige DOES matter?

[pinkjimiphoton]

So I guess sige DOES matter?

[D_Ex_Patria]

I got curious and added these on to my last DigiKey order.

I wired these them up as a hard clipper, and split a test sine through two buffers. The screencaps are from my USB scope.

RED signal is a pair of 1N914 diodes for comparison.
BLUE is a pair of SIGE rectifier diodes goobered onto vero with solder.

I did this with 1k and 10k series resistance, just to see if there was going to be a difference.



10k series resistance


1k series resistance

Honestly, I was hoping for something a bit more dramatic. As expected, they clip sooner than 1N914s, but aside from that, I can't see any magic Ge softness to the waveforms.

Maybe I'm missing something in my test.

Goobered SIGE rectifiers for those interested:

[Rob Strand]

I got curious and added these on to my last DigiKey order.

I wired these them up as a hard clipper, and split a test sine through two buffers. The screencaps are from my USB scope.

RED signal is a pair of 1N914 diodes for comparison.
BLUE is a pair of SIGE rectifier diodes goobered onto vero with solder.

I did this with 1k and 10k series resistance, just to see if there was going to be a difference.

Great work.

Those diodes look like they clip harder than 1N914s.
The SIGE diode threshold voltage is lower which is to be expected to some degree.

See,
https://www.nexperia.com/products/diodes/automotive-diodes/automotive-silicon-germanium-sige-rectifiers/#/p=1,s=0,f=,c=,rpp=,fs=0,sc=,so=,es=

I haven't read up on it but the "high thermal stability" isn't so clear to me.  At low currents they seem to have similar Vd tempcos to normal diodes.   And it's normal for the tempco to drop as the voltage drops get towards 1V (the band-gap voltage), which occurs at higher currents.  [Well, looking into it it might be referring to the low leakage, which remains low at high temperatures.]

[Rob Strand]

Check out,
https://www.electronicproducts.com/sige-rectifiers-deliver-high-efficiency-thermal-stability/

"The extremely low-leakage devices (<1 nA) offer an extended safe operating area with no thermal runaway up to 175°C."

[The implication is the Vd tempco remains negative upto at least 175degC.  If the Vd tempco goes positive the power dissipation VD*ID increases and the diode gradually gets hotter and hotter then fails. 
However, the aspect promoted is breakdown under reverse bias.
https://www.digikey.com/en/articles/use-sige-rectifiers-for-high-efficiency-ac-dc-operation
]

[D_Ex_Patria]

Yeah, the brochures do seem to hammer that intent home. I was hoping, as with many things, that there would be unintended side-effects, but it looks like the only thing different in this environment is the clipping threshold. The floor is open to suggestions.

Maybe I should be putting a tiny heater in there with them? 

[Rob Strand]

Yeah, the brochures do seem to hammer that intent home. I was hoping, as with many things, that there would be unintended side-effects, but it looks like the only thing different in this environment is the clipping threshold. The floor is open to suggestions.

Maybe I should be putting a tiny heater in there with them? 

It's not important for an audio clipper.

All diodes and transistors have an inherent Vd/Vbe tempco.   It's typically around -2mV/deg C; fine details excluded.   You can use them as temperature probes (accuracy around 0.3 to 0.8 degC over 0C to 100C).  I've probably got 1000 or more measurements I've made over the years testing these types of probes!  The idea goes back to the 1960s or before.

For power electronics the motivation is different, see prev post.  (I'm now 100% on the same page as the SiGe claims)