Negative logic

Yes, my error, realized that after pressing send, you use a grounded base PNP. Just to talk myself out of it, this works just as good or better with the NPN:

formatting link

The zener is optional, for a -5V supply you do not need it.

It is 'better' as the negative edge speed is set by the transistor going 'on', not by the collector resistor as in your circuit. That is if he needs that ..

Reply to
<698839253X6D445TD
Loading thread data ...

John Larkin wrote

And in every electronics shop here.

Reply to
<698839253X6D445TD

Hmm OK thanks Jan. Well maybe no zener, but how about a few diodes just to make sure the npn is off.

George H.

Reply to
George Herold

We don't buy production parts from electronics shops.

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
 Click to see the full signature
Reply to
John Larkin

Why use a transistor if all you need to do is shift into a CMOS gate?

Zener or bandgap, cap, resistor does it, and it's as fast as the driving gate.

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
 Click to see the full signature
Reply to
John Larkin

Sorry can you show me what you mean?

I'm doing this, which works fine.

formatting link

george H.

Reply to
George Herold

What about using some isolating coupler, like ADUM or Silabs Si8xxx?

--
Uwe Bonnes                bon@elektron.ikp.physik.tu-darmstadt.de 

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt 
 Click to see the full signature
Reply to
Uwe Bonnes

John Larkin

You steal those?

Well I consider digikey and mouser and the like just electronics shops. Same for ebay.

:-)

Reply to
<698839253X6D445TD

Sure. Depends on the voltage of the negative rail. But your RC diode circuit is of course the simplest solution.

Reply to
<698839253X6D445TD

John Larkin

Bit hard to get a 5.0 V zener (tolerances).

You can just do it with a RC and diode too.

Reply to
<698839253X6D445TD

Authorized distributors sell real parts. Small shops and ebay can sell you anything, and a long-term supply isn't assured. Distributors send us EOL notices so we can plan ahead.

There are entire towns in China that are in the fake components business.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

That's fine if you have short positive pulses and don't need DC coupling. To get DC, put a 5 volt zener or bandgap across the cap, and then you don't need the clamp diode.

You can probably skip the diode anyhow. HC logic has pretty good ESD diodes on the inputs.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

A 5.1 5% would be OK here, but a 5 volt bandgap would be better.

I think George is doing that.

Why not shift the output of the gate, instead of the input?

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

With current HC or AC or Tiny parts, paralleling sections works fine. They are well matched internally. Actually, we parallel multiple Tiny triple buffers, and that works too. If you source terminate, you can split the 50 ohm resistor into sections, one for each triple buffer.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

You don't get the full logic swing with a resistive shifter, so the driven gate can oscillate or go linear and get hot. The slow transition can cause shoot-through problems too.

With +5 and -5 supplies and equal resistors in the shifter, the lower gate sees +2.5 and +5 logic inputs relative to its Vee. Not good.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

John Larkin wrote

yes

That would work too, I always like to see the total picture.

Reply to
<698839253X6D445TD

John Larkin

i wonder, really, sure some cases you need to have a second source, some case ... But with a new chip coming out every week, how long are things available? That is one reason I like Microchip PICs, even the antique ones are still available.

I know, ebay: I have some bad MAX232, and LM35s that were clearly something else (got money back had the seller test it).

Smartphones are 'old' every 2 years, like cars...

It is a moving thing.

One should then design so the circuit does not so much depend on the parts used, that was the old way to design too, accommodating huge tolerances, you made the circuit so it could handle that. That is also why trimcaps and trimpots..

Took me a while to find a replacement LCD display with the same controller for something I designed, ebay helped out again. Else you need to rewrite the code.

More modular, so you can change a module if something fails, no matter what is in it.

Anyways, it is philosophy, if customer.. The Customer Is Always Right sort of thing. :-)

On that subject, I canceled my cable subscription yesterday, got fed up with their defective website interface and billing. Looks like I will go wireless, and then again ebay prices for the routers are half of what they charge here, The Customer Is King. :-) Now they should hurry up with that 5 G!

Reply to
<698839253X6D445TD

Everything, including computers and TVs and cars and printers and cameras and phones and, well, everything, should be one wireless 5G network. We're still in the Dark Ages of computing.

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

OK I see the zener, but what's a bandgap? Some two terminal device I don't know about? Oh like the LM4040... What the heck is inside those things?

George H.

Reply to
George Herold

You seem to believe in the 5G marketing BS.

Most of the fine features will only be available, when the nearly 30 GHz band is actually in use and there is a base station/access point in every light pole (small cell, good frequency reuse and manageable RF path loss: -).

Reply to
upsidedown

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.