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From: Jeroen Belleman <jeroen@nospam.please>
Newsgroups: sci.electronics.design
Subject: Re: AI
Date: Sat, 11 Jan 2025 00:10:55 +0100
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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:
>>>
>>>       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