Electronics Design does it Again!

Like i have said before, that is why i gave up on it near 30 years ago. It has not got any better.

The capacitor is there to provide an AC ground. The 'DC' (low frequency) amplification also depends on the potmeter. Video signals do not have a fixed DC level so you might be in for a bit of trouble if you use this circuit. Just add the capacitor and some resistors to mimic the pot and run an AC analyses.

The circuit would be okay if a second opamp is used to provide a solid reference voltage. This turns the circuit into a classic non-inverting summing amplifier hardly worth publishing. Actually this solution will be smaller since the capacitor would be fairly large anyway.

On a sunny day (Thu, 13 May 2010 17:48:41 -0700) it happened John Larkin wrote in :

How many asked if it was germanium or Si? Would be my first question.

Got an address so we can check it out on Google Earth?

So, now ED stands for Electronic Dysfunction?

I don't think I should do that. His habit of collecting rusty VWs is something he's written about in his columns, so that's already public. His address, and anything I know about him locally, is a private matter.

John

As long as you don't care about gain accuracy or frequency response, and as long as you don't use more than about a third of the pot rotation.

But everybody here has missed his real blunder: using a Maxim opamp.

John

You didn't model the pot as a pot.

Turn the pot all the way to 5 volts and replot the output.

John

Seeing as his summer job is with Maxim, I'd call it a politically astute move.

Could be _both_, or perhaps neither- such as a III-V material (but I'm not sure where to buy the latter in a discrete BJT).

I posted a DC restorer here a while back, AC-coupled input, sync tip clamped to ground. ...Jim Thompson

Here 'tis...

'Electron Deficiency' ;-)

An interviewee could certainly ask questions, or mention assumptions.

Can you still buy germanium transistors? Would that affect many of the answers much?

John

There are a few discrete HBTs for sale. Haven't tried them.

John

You can buy germanium transistors in China if you need them. It is kinda nostalgic to see old style metal cans.

BTW, on the matter of Jan's questions: 90% of experienced EEs think that Vce is 0.6V for silicon BJT in saturation mode. This misconception is surprisingly common.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Really? I didn't know that 90% of EEs were that dumb. That's terrifying.

I recently did some saturation measurements on a BCX70 and was surprised myself... but at least I didn't expect 0.6.

ftp://jjlarkin.lmi.net/BCX70_curves.pdf

I bet few EEs know how to make an NPN saturate to exactly 0 volts.

John

On a sunny day (Fri, 14 May 2010 08:47:22 -0700) it happened John Larkin wrote in :

Yes.

Yes

Especialy for you who thinks in femtos.

Show us, John. ...Jim Thompson