From: Winfield Hill
Subject: Re: how to master electronics, use of transistor, op amp...?
Date: 1 Nov 2002 19:36:20 -0800
Organization: Rowland Institute
References: <3DC282F0.firstname.lastname@example.org> <3DC2E327.email@example.com>
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> Wafer 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.