Unusual Bias Method

I saved it, but haven't looked at it yet. because the app that reads .pdf's if opened while the browser is being used hangs the whole system! and then when not on line, I'm not at the computer, I go work on the house, but soon, some day.

I know... I'm hanging chandeliers right now myself ;-) ...Jim Thompson

On a sunny day (Sun, 24 Nov 2013 08:53:30 -0700) it happened Jim Thompson wrote in :

I did my part of transistor amps, The usual way is a power limiting current limiting thing,

That would make it a bit primitive, sat before 1967?

As in...

If I ever designed anything that ugly, I wouldn't treasure it in my archives, and certainly wouldn't post it in public.

But you've got to admire the view.

--

John Larkin Highland Technology Inc

Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators

Ewww, PWM bias / current limit.

Mine's better (and I'm younger than you were back then).

Tim

-- Seven Transistor Labs Electrical Engineering Consultation Website:

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

It's not PWM, it's a linear amp. I suppose it was h-bridged because it wastes so much of the power supply's potential swing.

And right, the short-to-ground situation is grim.

--

John Larkin Highland Technology Inc

Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators

Must be your google, it displays upright here. ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

What you mean is, you don't understand how it works.

Now you'll bloviate and claim you do, but you'll _never_ post an explanation here. ...Jim Thompson

Oh, I freely admit that it makes no sense.

When the LM311 pulls low, all it does is reduce the quiescent bias, the voltage across Q5+Q6. What good does that do? What saves Q10 if the output is shorted to ground?

"John Larkin" wrote in message news: snipped-for-privacy@4ax.com...

LM311 is a comparator, with rather high gain at that. It ain't linear. The massive 20uF cap on the bias node keeps the rest of the circuit smooth but the comparator output will be PWM. Shitty PWM at that, there's no hysteresis, so the noise margin will suck near threshold (which depends on signal level besides).

Tim

"Jim Thompson

Attempting to *automatically* set and control idle current in a horribly thermally unstable output stage WITHOUT the use of temperature sensing is doomed.

Complementary emitter follower darlingtons ?

Powered from a 12V battery ?

Be lucky to see a 6V swing into a load.

.... Phil

What you mean is you freely admit you don't know how it works.

Only government employees are able to short outputs to ground, when the output is totally contained within the speaker box. You're just throwing sand in the air to obfuscate. Besides, each box was fused individually... which is "standard engineering practice" in an automotive environment >:-}

We need someone out there who can think "freely" outside the box. The bias does something unusual.

Can you figure it out before some 20-year-old shows you up? ...Jim Thompson

Ummmm..in the olden days it was not unheard of to use a comparator as an error amplifier by use of heavy dominant pole compensation.

I don't exactly know what the bias does, but my guess is it folds back as the VCC increases.

Cheers

LOUD BUZZER! That's not what it is, but I think Bloggs is onto something. I'm sure he'll solve it before Larkin has a clue. Larkin is a "cut and paste engineer" who denigrates "standard engineering practice", so he'll stay up all night tonight trying to figure it out... or one of his underlings will solve it for him, then he'll claim the solution as his own >:-} ...Jim Thompson

Think more subtly... start off with no signal, output flat-line, then work your way up from there. And think discontinuous behavior. ...Jim Thompson