Quote from: KE7GKP on June 21, 2011, 06:55:31 PM
There is no effective way of "patenting" an electronic circuit. As soon as you substitute one component or change a resistor value, it is a different circuit.I don't think this is true. For example, you can change the resistor value in a low-pass filter and the circuit is still functionally a low-pass filter. If you want to make a different circuit, I think you need to significantly change the way the circuit functions and/or accomplish something the original design does not. I'm not an expert on patents, though, so I could be wrong. All I know is I'm skeptical of your claim that patenting circuits is entirely ineffective.
I own several patents myself so although not a legal expert, no noob either but all disclaimers apply 
First legal rules wrt patents differ per country and are even subject to change, and are not respected in all countries either ...
- Electric circuits can be patented, but they should be really new AND solve a real problem (there are definitely some degrees of freedom wrt what a problem is)
- Using a known electric circuit (low pass filter) as a new solution for an exisiting problem can be patented if it is not a trivial solution (there has to be some inventiveness in it)
Bens is right that a non significant change in a schematic still falls under the patents protection. I think all patents I've seen claim that trivial changes to the proposed solution are part of the claims. Sometimes the claims go so far that they claim the solution to be new and that the implementation can be either software and/or hardware implemented. (a lowpass filter can be made in many ways!)
Wrt Patents:
Patents normally consists of 4 parts: (1) a problem description, (2) the state of art solutions/prior technology, (3) a proposed new solution and (4) claims. For the legal people the claims are the farmost important as that is what is claimed, second the state of art is important as that decides if the proposed solution is really new or not. If you failed to find/describe all earlier solutions it might be that your solution is not new at all (this happens very often!)
Getting a patent is not easy but after "the bright spark" and the necessary work (literature research/editing/rewriting etc) it can be done. The real difficult part comes then, to enforce your patent. If someone else uses your patent you get in a legal fight and you have to proof someone is using your patent. If the other party can show it make things that way before your patent was filed => say bye to your patent as the work of the other party is prior technology. These legal fights are very costly and often difficult to win. Some would say only the lawyers win ...
Proofing someone else uses your design in electronics is quite difficult as you often need to be able to reverse engineer chips these days. That makes it difficult to enforce your rights, so often it is easier (and economical more interesting) to keep the design secret and use your money to be the first in market and fill up all the sales channels. And if you patent something, don't patent a specific solution, try to patent a generic (implementation independant) one
That said, for real patent advice contact a patent attorney.
my 2 cents,
Rob