Re: AI

On 1/10/25 23:41, Cursitor Doom wrote:

On Fri, 10 Jan 2025 22:28:40 +0100, Jeroen Belleman wrote:
 

On 1/10/25 20:37, Cursitor Doom wrote:

Gentlemen,
>
I've just been goofing around with X's AI assistant, Grok. After
feeding in a few straightforward questions and getting surprisingly
impressive answers, I decided to try something a bit more subjective to
see how it would cope. Here's what happened...
>
>
My question:
>
Which of the common 'classic' oscillator designs is the most impressive
or ingenious from a technical standpoint?
>
Grok's Answer:
>
  From a technical standpoint, several classic oscillator designs stand
  out
for their ingenuity, but one that is often highlighted for its elegance
and versatility is the Colpitts oscillator. Here's why:
>
Design Ingenuity:
>
      Simplicity and Efficiency:
          The Colpitts oscillator uses a simple configuration with a
transistor (or vacuum tube in older versions) and a combination of
capacitors and an inductor to create a feedback loop. Despite its
simplicity, it achieves stable oscillation with just a few components.
      Feedback Mechanism:
          It employs a capacitive voltage divider for feedback, which is
particularly ingenious. The two capacitors in series (C1 and C2) form a
voltage divider that provides the necessary phase shift for
oscillation. This method naturally provides the correct phase without
additional complex circuitry, making it both efficient and reliable.
      Frequency Stability:
          The frequency of oscillation in a Colpitts oscillator is
determined primarily by the LC tank circuit's resonant frequency, which
can be calculated as f=12πL(C1⋅C2)/(C1+C2)
          . This formula highlights how the design inherently stabilizes
frequency through the interaction of inductance and capacitance. The
use of capacitors in the feedback loop also helps in reducing the
impact of transistor parameter variations on frequency stability.
      Versatility:
          The Colpitts oscillator can be adapted for use across a wide
          range
of frequencies from audio to RF. By changing the values of L, C1, and
C2, one can easily tune the oscillator to different frequencies, making
it adaptable for various applications from radio transmitters to clock
generators.
      Low Noise and High Purity:
          When designed correctly, the Colpitts oscillator can offer low
phase noise, which is critical for applications like communication
devices where signal purity is paramount. The design inherently
minimizes noise by reducing the number of components in the feedback
path.
      Ease of Adjustment:
          Adjusting the frequency is relatively straightforward with
          minor
changes to the capacitor or inductor values, making it practical for
both prototyping and production environments.
>
>
Historical Context:
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      Invented by Edwin H. Colpitts in 1918, this oscillator was a
breakthrough in the era of vacuum tubes, which were later adapted for
transistor use. Its principles have stood the test of time, still being
taught and used today in various forms.
>
>
Comparison:
>
      While other oscillators like the Hartley oscillator (which uses an
inductive voltage divider) or the Clapp oscillator (a variation of
Colpitts with an additional capacitor for better frequency stability)
are also significant, the Colpitts design is often praised for its
balance of simplicity, efficiency, and versatility.
>
>
In conclusion, the Colpitts oscillator stands out for its impressive
combination of simplicity, effectiveness, and adaptability, making it
one of the most ingenious classic oscillator designs from a technical
perspective.
>
>

**************************************************************************

>
Any observations?

>
Yeah. The resonant frequency formula is wrong. To first approximation,
it's f=1/(2π sqrt(L C1 C2 / (C1+C2))). (Inline algebraic notation is a
dog...)
>
It looks like Grok has trouble reading formulae.
>
Of course, it doesn't really know what it's talking about.
It just ladles out some phrases it gathered from various web sites on
the subject.
>
Jeroen Belleman

 The formula error is not Grok's mistake. The sqrt didn't survive the
cut'n'paste I'm afraid. I didn't reckon on someone spotting that so didn't
mention it in the OP.

We need a new word for this kind of thing. I propose "plagiamaton",
meaning something like "agent that steals ideas".
For some of the more awkward phrases, I even found where it got
them from. For example, the phrase starting with "This formula
highlights..." seems to come almost verbatim from a particularly
poorly written web page by Keysight.
Jeroen Belleman