It's often said that modern electronics is based on quantum mechanics. As far as a I can tell however, detailed understanding of quantum mechanics isn't needed to, say, design a transistor. Although quantum mechanics sets a lower bound on the size of electronics, this would be obvious empirically anyway, and it seems that nothing beyond standard engineering and relativity actually has applications in most electronics, lasers, etc. In contrast to atomic physics and pharmaceuticals where it has extensive applications. Thoughts?