Normally we think of an amplifier as being something used to to increase output. But it turns out one of the most important and successful types of amplifiers is one that uses gain as negative feedback to oppose the original signal.
The negative feedback amplifier was invented by Harold Stephen Black. While on his way to work, he scribbled out the now famous invention on a piece of The New York Times newspaper. Black submitted his invention to the U. S. Patent Office on August 8, 1928, and it took more than nine years for the patent to be issued. Black later wrote:
“One reason for the delay was that the concept was so contrary to established beliefs that the Patent Office initially did not believe it would work.”
One reason the negative feedback amplifiers are so useful is that they tend to help stabilize signals. They act as a sort of electronic brake, reducing distortion and increasing overall control. When used correctly, it can create stability and help improve their operating characteristics.
Sometimes, something we think is a failure actually turns out to be a success!