2n5457 original ou fake?

andregarcia57 · Post by **andregarcia57** » 19 Jun 2023, 16:06

hello everyone,
I bought a lot of 2n5457 and I would like to know if there is a way to know if they are original or fake.
grateful follows reading one of the lot.

Manfred · Post by **Manfred** » 19 Jun 2023, 23:49

The way I interpret the displayed values means Id=0.18mA @126mV Idss ~ 0.18mA and Id=0mA @ 327mV Vgs(off) = 327mV.
According to the datasheet the range for Idss is 1mA to 5mA and for Vgs(off) -0.5 to -6.0V.
This means that the values of the measured FET are outside the tolerance range.

mediy · Post by **mediy** » 20 Jun 2023, 10:52

I had always thought that you can't reliably confirm these tested figures to most datasheets as the the datasheets specify particular test conditions and you can't guarantee that the conditions use by a tester like this are the same.

andregarcia57 · Post by **andregarcia57** » 20 Jun 2023, 11:22

I ended up putting it together to see if it sounded good in practice, I made a fuzzcentral buffer for my vox, I don't seem to have a big problem using it. but anyway it's very hard to find real components.

Bulldozerrr · Post by **Bulldozerrr** » 20 Jun 2023, 13:53

This device is absolutely inapplicable to measure parameters of the jfet correctly.
Original 5457 can has Ugsoff from -1.5 to -2.5 Volts. And Idss from 2 to 4mA.
I have not seen the new original 5457 in ТО-92 more then 5 years.
I guess that this jfet is fake.
If it was bought on Ali, then it 100% fake. However, the lot of Chinese sellers has occupied other places like e-bay. And they sell fake components.
And the schematic is incorrect. Even original 5457 will not work properly.
Because Ugsoff is insufficient for this purpose.
This source follower is suitable only for relatively small signal levels.

However you can use the fake 5457 in source follower in your schematic.
Just add one additional resistor 1M from +9V to gate.

andregarcia57 · Post by **andregarcia57** » 20 Jun 2023, 17:17

Got it, anyway I'm going to do a JFET tester today to check some.

OBS: this lot I bought is from 2016, it was in the other house.

andregarcia57 · Post by **andregarcia57** » 21 Jun 2023, 21:03

I found one here, in a used parts box, 2n5457 bought in smallbearelec, true...

george giblet · Post by **george giblet** » 21 Jun 2023, 23:57

What you really need to do is build your own tester then compare the results against the TC1. I don't have much faith in component testers for JFETs. In some cases what they report is "true" but only if you know how to interpret what the numbers mean. In many cases they don't report the IDSS and VP values.

In your case it doesn't even look correct as the ID @ VGS is less than IDSS. No ID @ VGS result can be greater than IDSS.

Got it, anyway I'm going to do a JFET tester today to check some

That "tester" is OK for matching but not for extracting the JFET VP parameter.

Can I suggest the simple test set-up on this page. Section 11 at the bottom. It does both VP and IDSS.
https://runoffgroove.com/fetzervalve.html