Nobody likes negative feedback. We humans prefer constructive criticism. But when applied with attention and care, it can help make things better. A mediocre amplifier without feedback can be turned into a great amplifier by applying negative feedback. So, what exactly is feedback, and who invented it?

What Is Feedback?

On August 8, 1928, American electrical engineer Harold Stephen Black (1898–1983) filed a complicated patent for a “Wave Translation System”. The first claim reads as follows:

1. In a wave translating device or system having amplifying properties, an input portion and an output portion, means to apply fundamental waves to said input portion, said system carrying fundamental components in said output portion and having means producing other wave components in said output portion, and means controlling the relative magnitudes of said components in said output portion comprising means to feed waves from said output portion to said input portion to decrease the g...