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Subject: Re: how to master electronics, use of transistor, op amp...?
References: <3DC282F0.firstname.lastname@example.org> <3DC2E327.email@example.com>
Date: Sat, 02 Nov 2002 11:35:05 GMT
NNTP-Posting-Date: Sat, 02 Nov 2002 06:35:05 EST
Organization: Road Runner
Well, this sounds like an interesting little circuit. I actually
don't usually approach a design from this prospective either. Again, I'm
self taught, and although it has obvious advantages to me, it typically
means that my approach is to solve a particular need. What this normally
requires is some understanding of the purpose of the circuit, not in
turms of specs on paper, but in the real world application. Something
like: here is a signal that need to get through a 50FT. cable with no
more than so much loss. The signal can't see an impedance of less than
x, and must arrive at the other end with as little distortion as
possible, etc, etc.
You see, I simply skip most of the calculations and just put
together something that would probably have at least fair performance,
then tweak the thing as needed. In the case of your circuit
requirements, I can see that simply using a standard breadboard would
screw up the whole thing. Stray capacitances alone would see to that.
In any case, this entire discussion is not about my skill, talent,
or anything else. It's not about any one person at all. The thread was
started by someone asking how one goes about "mastering electronics",
and asked for others to share experiences. That's what I did, and if I
knew it would turn into a contest, I would not have responded as I did.
Winfield Hill wrote:
> Winfield wrote...
>>> Please don't confuse skill with talent. Skill is acquired over time,
>>>and involves much work and effort, while talent is there from the very
>>>beginning. However, lets not get tied up with semantics. I suppose I
>>>should have also pointed out my obsession with electronics. ...
>>> [ snip ]
>>> I would have to say that since Stephen William Hawking concerns
>>>himself with theoretical physics and such, he may not be an appropriate
>>>example of someone who would (or could) design an electronic circuit in
>>>his head. Besides, it's not a matter of mathematics, or some enormous
>>>number of calculations. Rather it is something which I actually find
>>>difficult to put into words. I just do it. ...
>>I find it difficult to design electronic circuits without extensive
>>calculations, maybe not always written entirely on paper, but either
>>performed in my head or using an ever-present pocket calculator, and
>>with the results appearing on paper in one growing schematic drawing,
>>or in a set of drawings representing different possible approaches.
>>So, it's very hard for me to comprehend designing viable circuits
>>without any schematic at all, either on paper or in computer file.
>>Perhaps you'd like to try your hand at a design I'm completing now,
>>a quiet transresistance preamp (current-to-voltage) that presents
>>5pA current steps as 0.5V voltage-step outputs with a response time
>>of 10us or better, with 100pF node capacitance. We'll have to also
>>assume you already know the component's parasitic properties to make
>>the appropriate selections and modify the design accordingly, right?
>>If you quickly finish the design, you'll have time to design a test
>>fixture to verify its impressive performance.
>>To my mind this type of relatively-simple design cannot be achieved
>>entirely in one's head, so it should be a good test for your skill.
>>Remember, be honest now, no paper or computer allowed for this test.
> Oh, wafer, a few other circuit specs for this test. My circuit has
> only two 8-pin ICs, makes measurements to 10fA without requiring any
> adjustments or calibrations, and drives a 50-foot cable. The two ICs
> are inexpensive parts that have been available for several years.
> - Win