Greetings all.
Needing a fast small signal diode for a peak detector, I obtained a couple of NTE109's - packaged individually in carefully labelled plastic bags.
The NTE109 is claimed to be a germanium, fast switching general purpose diode.
I did a simple test (simple half-wave rectifier, loaded with a 2K7 resistor) at 500kHz and to my unpleasant surprise it performed identically to an 1N4148 (testing with a schottky diode for comparison provided a much better recovery time)
I measured the forward voltage drop to around 0.6V with a multimeter - expecting 0.3V from germanium.
This smells standard silicon, but at a (at least) 20 times price tag.
The case (apr. double length of an 1N4148) has no markings, which might indicate something is wrong (even an 1N4148 can have a '4148 printed on the available space).
So my question is now (before contacting the dealer): are NTE109 known victims for fakes?
Cheers
Martin
Needing a fast small signal diode for a peak detector, I obtained a couple of NTE109's - packaged individually in carefully labelled plastic bags.
The NTE109 is claimed to be a germanium, fast switching general purpose diode.
I did a simple test (simple half-wave rectifier, loaded with a 2K7 resistor) at 500kHz and to my unpleasant surprise it performed identically to an 1N4148 (testing with a schottky diode for comparison provided a much better recovery time)
I measured the forward voltage drop to around 0.6V with a multimeter - expecting 0.3V from germanium.
This smells standard silicon, but at a (at least) 20 times price tag.
The case (apr. double length of an 1N4148) has no markings, which might indicate something is wrong (even an 1N4148 can have a '4148 printed on the available space).
So my question is now (before contacting the dealer): are NTE109 known victims for fakes?
Cheers
Martin
The current data sheet for the NTE109 (Rev. 4-20) does not indicate germanium or silicon, just a fast switching general purpose diode.
I suppose it's possible it was germanium in the past, but with a Vf max spec of 1.0V I would also suspect it's now silicon.
NTE parts are sold as replacement parts, mostly to the repair industry, so they tend to have rather broad, general specifications and are individually packed and fairly expensive compared to volume pricing.
I have purchased many over the past 20 years and never seen any I would consider fake, but these days it seems nothing is exempt.
I suppose it's possible it was germanium in the past, but with a Vf max spec of 1.0V I would also suspect it's now silicon.
NTE parts are sold as replacement parts, mostly to the repair industry, so they tend to have rather broad, general specifications and are individually packed and fairly expensive compared to volume pricing.
I have purchased many over the past 20 years and never seen any I would consider fake, but these days it seems nothing is exempt.
I know you used to be able to get ECGs that were Ge at one time, but I’m not sure the 109 ever was. I seem to recall a 2-digit type number for the 1N34/1N60 equivalent. NTE gets whatever they can get - and if fakes are all they can get thats what you get - so for anything rare or out of production its buyer beware.
If you can’t raid an old radio for a Ge diode, I’d just try a schottky. That often works just fine in radios that took Ge’s originally. If Vf is important, don’t look for the smallest tiniest one - Vf goes up at “high” currents. Since there is no Trr, you might be able to live with higher CJ than equivalent Si (or Ge).
If you can’t raid an old radio for a Ge diode, I’d just try a schottky. That often works just fine in radios that took Ge’s originally. If Vf is important, don’t look for the smallest tiniest one - Vf goes up at “high” currents. Since there is no Trr, you might be able to live with higher CJ than equivalent Si (or Ge).
Thanks for the answer.
Now, that is interesting.
The datasheet (attached) I found from the same vendor says Germanium.
And the plastic bags used for the individual packaging says "Ge, General Purpose Diode".
You are right about the Vf max - but given it is measured at 3 times more than the maximum If, it would depend on the resistive part of the diode construction.
So it may not be a fake, but rather a "buy, and see what you get" 🙂
I will though return the components as they were sold as "Germanium".f
Cheers,
Martin
Thanks for your answer
The aim is purely speed - and as I described, I did try with a schottky diode and even if not being the fastest around (BAT46) it performed significantly better than the 1N4148.
I plan to get hold of some BAT41's which according to the datasheet should be faster.
Cheers,
Martin
Very few parts from NTE would I consider buying. Transistors for an audio circuit are not one of them.
Thanks, I see what you mean - and to some degree the very impression the plastic bags gave was one of old days; not quality.
Well, I got wiser - not richer nor happier
Cheers,
Martin