Re: Twin T circuit wanted

Thanks, John. I like the bong! But it's a little on the long side tho, don'cha think? That's one problem with perfect inductors and capacitors, too high Q. How about adding some esr loss for the inductor, or a parallel resistor on the LC tank?

I wonder, don't we need a bypass capacitor on Q2, the oscillator-supply voltage emitter follower? Check out the waveform there. And of course, then we'll need a Q2 base resistor to help stop the RF oscillation thing - you know, the old emitter-follower with cap load, etc.

I installed 4.07x on this machine on May 30.

Best regards, Spehro Pefhany

Thanks! Sounds nice - now, whereinthehell is the icon for a "bongy" face? :-)))

Ed

It's recursive mumbling, the sound you make when you mumble "mumble."

John

Yes, John... muMble is a word.

"muNble", which is what you wrote, is not, idiot.

That's nice. It's running pretty hard class C.

Try this:

C2 = 10 uF L2 = 0.25 uH

That will move it to class A, with about 50 millivolts p-p drive at the emitter. That's more like what I had in mind originally. Vb is stiff at about +0.6, and Vc dips down to about -0.1, a little below Ve, sucking a brief blip of current out of the base cap. The sine wave is just slightly flattened on the bottom.

It's useful to add a small resistor, like 1 milliohm, in the emitter so that you can probe the current. It's interesting.

I measure the amplitude at the collector at 10.11 p-p, pretty close to

ftp://jjlarkin.lmi.net/LC_YDx.gif

John

Everybody must know the less obscure case by now.

The more obscure case: In the toob days, sometimes TV sets would have vertical bars on the screen. It was caused by Barkhausen oscillations in the horiz output tube, getting back into the RF input. Some TV techs called that "squegging."

I have no idea of the source of the word.

John

The .wav thing is cute. But the ringdown is being caused by the LC's Q, not by the transistor oscillation. The R2-C4 thing dies out pretty soon, and then the tank rings on its own. That why you need R4; at infinite Q, it would ring forever.

If you can get an LC with a Q that high, you can simulate a nice bell noise by just whacking it and letting it ring... like a real brass bell. Much simpler.

John

One ringy dingy.

Hi John,

You don't need to add the the resistor. You can just measure the emitter current by clicking on it!

...

Works fine here. version 4.07q

--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---

add external negative resistance.

--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---

Mine updated itself a while back, just checked --> 4.07.

Grant.

the

=3D 120mV

did that

posted

So you like red beards.?

I couldn't get that to work. Maybe my aim isn't good enough.

John

I chose the wrong extension to name the file with.

Mine is 4.07z

They do auto-update, but not on every run. So, you may still have the one you loaded originally.

John Larkin Inscribed thus:

I've always thought (a burst of oscillations at regular intervals) probably from the sound made when a radio squegs.

AlwaysWr AlwaysWrong> LTSpiceIV just came out today!

Wrong, as always.