LC circuit

[Don Bowey]

HI Bob,
Good question:
One of the thing I am trying to do well.
I can only explain well using an analogy.
You get on a swing set, you generate enough energy so that you start swing
(oscillating) everutime you reach a peak value, you give yourself (or a
friend..) a small push to keep going the same amplitude.BUT if you keep
giving the same push everytime with the same strenght you did the first one,
you will reach a point where you will no longer get to go any higher, or
simply break and fall. In an oscillating mechanical system when you reach
that point, the machine simply over heat or break down. This is what I want
to do electrically.

K

I'm late getting into this string.... It sounds to me as though you want the
electronics to self destruct. Is that correct?

Here you are.......

1 - Amplifiers make good oscillators. No amplification, no oscillation.

2 - If you provide *enough* positive (in-phase) feedback an amplifier *will*
oscillate.

3 - At a feedback amplitude that is very near, but below, what it takes to
cause sustained oscillation, the amplifier will ring or ping with noise.

4 - Increasing the positive feedback beyond that in item 3, you can drive
the amplifier as hard as you wish, up to self destruction if you pick the
correct components.

You can make an amplifier oscillate with, or without the LC network. The
tuned circuit just lets you set the frequency at which you want (or hope
for) it to oscillate.


Don

 

[Rich Grise]

HI Bob,
Good question:
One of the thing I am trying to do well.
I can only explain well using an analogy.
You get on a swing set, you generate enough energy so that you start swing
(oscillating) everutime you reach a peak value, you give yourself (or a
friend..) a small push to keep going the same amplitude.BUT if you keep
giving the same push everytime with the same strenght you did the first one,
you will reach a point where you will no longer get to go any higher, or
simply break and fall. In an oscillating mechanical system when you reach
that point, the machine simply over heat or break down. This is what I want
to do electrically.

You've just described an oscillator, almost perfectly. Try some of
these links - injecting a little energy each cycle is exactly what
oscillators do, and they go to the rails unless there's some kind of
negative feedback - the "Wein Bridge" (Wien?) is a good example of that:
http://www.google.com/search?hl=en&q=oscillator+tutorial

Cheers!
Rich

 

[Bill Bowden]

I can only explain well using an analogy.

You get on a swing set, you generate enough energy so that you start swing
(oscillating) everutime you reach a peak value, you give yourself (or a
friend..) a small push to keep going the same amplitude.BUT if you keep
giving the same push everytime with the same strenght you did the first one,
you will reach a point where you will no longer get to go any higher, or
simply break and fall. In an oscillating mechanical system when you reach
that point, the machine simply over heat or break down. This is what I want
to do electrically.

Well, you could use a L and C in parallel from the gate to ground of a
JFET. Wind a few turns of wire around the L and add a resistor in
series and connect the wire to ground and the other side of resistor to
the source of the JFET. Connect the drain to +V, turn it on and there
will be a nice sinewave at the gate. You can adjust the amplitude with
the resistor. Requires 4 parts plus battery.

-Bill