2n5457

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2n5457

Post by ef37a »

JFETs, had to buy a pack of ten to get one so if anyone is in real need give me a PM and I will pop one in an envelope for them.

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Re: 2n5457

Post by Folderol »

Don't have a need for one, but out of curiosity looked up their spec. Not bad, but quite high gate leakage by today's standards.
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Re: 2n5457

Post by ef37a »

Folderol wrote: Sat Oct 30, 2021 7:42 pm Don't have a need for one, but out of curiosity looked up their spec. Not bad, but quite high gate leakage by today's standards.

Well, if you are going to be picky Will. NO free FETs for you!

Heh, I just need to knock up a very basic guitar pre amp for a little project I am working on as a present for my daughter's partner on his birthday.

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Re: 2n5457

Post by Martin Walker »

I think the last time I soldered in a FET it was a 2N3819 (does that date me?)
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Re: 2n5457

Post by N i g e l »

WOW ! this is spooky, I recently replaced some J112's in an Alesis Microns power_on_click_silencer / general_output_knackerer circuit.
Maybe there's a FET virus......
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Re: 2n5457

Post by Folderol »

Martin Walker wrote: Sat Oct 30, 2021 9:17 pm I think the last time I soldered in a FET it was a 2N3819 (does that date me?)

Yes :lol:

Oh, and I left the one in my signal generator severely alone (if it ain't broke, don't fix it).
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Re: 2n5457

Post by ef37a »

Martin Walker wrote: Sat Oct 30, 2021 9:17 pm I think the last time I soldered in a FET it was a 2N3819 (does that date me?)

Yes! I used a pair in a cascode band ll pre amp before we got the Boughton Green Road repeater.

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Re: 2n5457

Post by Martin Walker »

I'm definitely old then ;)
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Re: 2n5457

Post by ef37a »

Just FYI chaps. I built the pre amp, circuit called for a 6k8 drain load and a 2k2 source 'bias' resistor. The FET did not pull nearly enough current from a 12V supply (Vdrn too high) I had to reduce the source R to 270 Ohms to get Vdrn near 1/2 supply.

Hooked into the gadget I built it for however, on a 23V supply it gave plenty of clean gain and low noise when tested with a Strat clone.

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Re: 2n5457

Post by Folderol »

Good to see you got it working. Bias voltage on older FETs was always a guessing game. It's rather given away by the cut-off voltage spread. I just looked it up for that one and for fairchild (one of the good guys) it's -0.5 to -6!
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Re: 2n5457

Post by ajay_m »

The process by which jfets are made intrinsically results in much higher parameter spreads than for bipolar transistors. Consequently it is sometimes necessary to test several devices to find e.g a reasonably matched pair. There's a good discussion of this in "the art of electronics", a book well worth acquiring if you're seriously interested in circuit design.
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Re: 2n5457

Post by tubegeek »

Beware of counterfeit FETs, especially through-hole parts common for audio, guitar pedals etc. They are rife. Ebay & Amazon are very hit-or-miss in terms of authentic items.

If they are too cheap to be true, they are too cheap to be genuine, in my experience.
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