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I've been thinking of making a database / program to make building analog circuits easier. I wanted to make sure there isn't anything else like this that I can contribute to instead of going through the effort of creating something from scratch. Lets see if I can describe what I am thinking about in my head in words:

With this program or database you would be able to select a type of circuit block and enter the desired specifications of the circuit. The solver would then automatically determine the resistor values, capacitor values and components necessary to meet the specifications set.

How about an example? Let's say that I want to design a BJT common emitter amplifier like the one:

enter image description here

When designing an amplifier like this I really only care about a few things and don't always want to go through and calculate everything every-time. I would input the maximum AC voltage in, the output impedance of the previous stage, the positive and negative rail voltages, and the desired voltage gain / current gain. In turn, it would be able to solve for the resistors & capacitor values needed and if it was REALLY cool, suggest a few transistors that would work for it.

Disclaimer - I'm sure I missed something...

Now with a simple circuit like this you may think, "Is this really necessary?" My answer to this is, not really. But imagine if you could now select these blocks, connect them together and design entire circuits. I have been thinking about using Falstad circuit simulator or circuit lab and some html scripting for this. There are many other things in my head right now about this, but I will keep them to myself to keep this post simple.

So, my overall questions are: Is there anything else out there like this that I can contribute to? Is this completely impractical? Would anyone else be interested in having a tool like this?

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  • \$\begingroup\$ Many IC vendors have tools that do essentially this, for a limitted application area. For example TI (formerly National) WebBench will spit out a switching power supply design from a small set of requirements. And LTSpice includes numerous template circuits that will let you quickly design a subcircuit like yours around a particular amplifier. Agilent has a (high-priced) tool called Gensym that will generate high/low/band-pass filters to spec using discrete components or microstrip elements. \$\endgroup\$ – The Photon Jul 30 '12 at 16:36
  • \$\begingroup\$ If you don't care about harmonic distortion, Noise Figure, power drain and efficiency, there are lots of cookbook designs for self bias, gain and output impedance. But there are a lot more specs than meet the eye with a simple discrete design. They use them in designing linear chips with discrete devices, but generally the experienced designer learns these tools are just to get started and you find out there are other critical parameters like propagation delay and gain bandwidth product. \$\endgroup\$ – user11355 Aug 8 '12 at 21:58
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I think you have good idea, however it already exists in some variations. I found one example for BJT cascode stage: http://www.daycounter.com/Calculators/Cascode/BJT-Cascode-Calculator.phtml

But also, I'm encouraging you to make it on your own way for few elementary different topologies, having in mind this few points: 1. it should be online; 2. it should be in pure javascript (not Java or Flash) 3. dialogs should be in schematic 4. SVG for that matter should be the markup language of choice

That's only my opinion. Good luck with this nice idea.

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It looks like I have found the answer. I haven't tried it (i'm about to) http://www.physicsbox.com/indexsolveelec2en.html It looks like you draw a circuit and it will make literal formulas for you :) I'll let everyone know how it goes! It's for mac and pc!

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  • \$\begingroup\$ It's pretty bad, but it is better than nothing. \$\endgroup\$ – OhmArchitect Jul 30 '12 at 12:32
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I can point you to two existing software that have similar functionality. I've used both and both are very good.

that circuit simulator http://www.falstad.com/circuit/ runs on Java, runs even in the browser itself. and this Android app https://play.google.com/store/apps/details?id=it.android.demi.elettronica several basic circuits and their calculations available there.

hope it helps.

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TransistorAmp could be an interesting solution to this problem. You simply input the criteria you want such as input and output impedance, bottom cutoff frequency, component series to use and gain and finally you select the transistor from a very large list. It will produce a circuit diagram and select appropriate values on its own.

Unfortunately, it only works for BJTs in common collector, emitter and base configurations and doesn't have much sanity checking (for example it will output a circuit that will start burning in seconds if user has unrealistic expectations of the transistor picked).

On the plus side, it's free,small, easy and fast to use and produces output in HTML. Here's an example of its output.

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