BCX70J curves

Oooh! Like page 2 curve. How about doing an inverted set?

Maybe so, just for fun. I didn't expect either of those curves, the little hook near zero on p1, or the general shape on p2.

Interesting that this transistor makes a pretty good constant-current dumper above about 0.25 volts.

John

On a sunny day (Thu, 22 Apr 2010 07:07:23 -0700) it happened John Larkin wrote in :

Is not that the same for most if not al BJTs? (Pethode chacteristic) "constant", in what way?

1) beta spread. 2) you drive it via a resistor from a constant voltage, so that needs stabilising 3) the Vbe drop is in series wih the drive voltage, and is temperature dependent.

Add a good opamp and a reference voltage.

4) I was just on the phone for almost an hour with the 'techies' that provide my net connection. Wonder if I can send them a bill for IT training.

'A name server, what is that?, oh, I may have heard of it, not sure we have one'. KPN telecom. Be afraid, very afraid.

BCX70s are binned pretty tight. A beta-limited BCX70J would be way more consistant a current sink than, say, a typical jfet.

stabilising

Stabilizing for what, and why?

dependent.

Not very.

Too many parts in the immediate case. I just need to sink roughly 1 or

2 mA from maybe 0.5 to 30 volts, switchable on/off from a uP, to load a source follower. But I'll probably use an LND250, because I can do that without the resistor.

one'.

We use LanMinds, an ISP in a little storefront in Berkeley. It's all geeks who will answer the phone during working hours and answer support-question emails at, apparently, any hour. They really know their stuff and, if you don't want to do what they say, they'll do it for you.

Have you tried the google name server? 8.8.8.8.

John

On a sunny day (Thu, 22 Apr 2010 08:27:17 -0700) it happened John Larkin wrote in :

For voltage, I = U / R, so if U changes, Ib changes, then Ic changes.

dependent.

OK.

Yes, FETSs make good current sources, but often the spread is huge for one type number, I do not know this particular one (have never used it), Looking at the datasheet it has 'not recommended for new designs' all over it in colored ink, also Rds on max is 1 k, at 2 mA it would drop 2 V worst case, so that would not meet your spec.

If this does not resolve really soon I may host my site in the US.

Yes I know about 8.8.8.8 and 4.4.4.4, but that is not how the system works. I am registered (domain) with go-daddy (US), that points to ip51cf87c4.direct-adsl.nl for authorative name server (my server), and that should resolve to

81.207.135.196 on the wxs.nl nameserver, the dns will then ask 81.207.135.196 port 53 (this computer) for all my services. Using 81.207.135.196 directly in go-daddy does not seem to be possible, gives an error. Was possible in the long ago past though. DNS is being revamped, with all sorts of encryption and protection being added. Maybe somebody at wxs.nl is rebuilding the servers (kpn routes through wxs.nl). Beyond my control?

The DNS mods have already caused big problems in the last few month in Europe.

Hey! I jsut see my test email from 8 oclock this moring coming through, testing the DNS now, it works again! Indeed some *censored* at wxs.nl must have played with the server. Well that hour on the phone may have helped too (and about 10,000 other users). OK, test website:

WORKS AGAIN! Wow, that saves a lot owf work (porting the site to where ever). Would it make a difference that I mentioned my law insurance to kpn? LOL maybe :-)

dependent.

number,

in colored ink,

meet your spec.

This is a depletion mode n-channel mosfet. Idss runs pretty consistantly around 1.5 mA. I can ground the gate and switch it on and off by hooking an open-drain port pin to the source. As I said, all I need is a current sink to pull down a mosfet source follower.

The SOT23 version of LND150 is essentially the same part. These depletion fets are great for front-end overload protection.

John

That "hook" is standard ho-hum; what is surprising is the flatness of the "curve" makes it look that Mister Early is rather late..

stabilising

dependent.

one'.

A "Name Server" is the local hotel bell hop trying to deliver a message for you..

dependent.

type number,

in colored ink,

not meet your spec.

Interesting. Could they be used for ESD protection while driving inputs to a MCU?

On a sunny day (Thu, 22 Apr 2010 23:23:55 -0700) it happened Robert Baer wrote in :

one'.

For some an 'apple' is some overpriced gadget, for some something edible. Things can have very different meaning in very different places. for example 'PIC' (as in micro controller), pronounced in Dutch as PIK, refers to the male sex organ. So if you were to say 'Ma, I am going to play with my PIC'. translated into Dutch as 'Ma, ik ga met mijn PIK spelen', you will get some funny looks.

Probably better to refer to it in Dutch as 'micro-computer'.

dependent.

type number,

it in colored ink,

not meet your spec.

The LND150 is rated to 500 volts, so it's not enough for ESD protection by itself. But a reasonable cap to ground ahead of it, a couple of nF maybe, will reduce ESD spikes enough to protect the LND. Two LND150s, each shorted S-G, back-to-back, make a gadget with about

2K small-signal resistance - not a huge amount of Johnson noise and no offset - but that will current-limit at 1 mA or so. That lets you build fairly low-noise amps that won't be damaged by line voltage.

Somebody should package a pair of depletion fets like this, as protectors. Better yet four of them.

John