American inventor and engineer Otis Frank Boykin had almost 30 patents including for the pacemaker! His largest contribution was the work he did on electronic resistors.

Via National Inventors Hall of Fame:

In 1959, Boykin invented his wire precision resistor and two years later invented an improved version that could withstand extreme changes in temperature and pressure. It was cheaper and more reliable than previous types and was in demand by the U.S. military, IBM, and other high-tech organizations. In 1964, he developed a control unit for pacemakers making possible their precise regulation. The advances made by Boykin meant many electronic devices could be made cheaper and more reliable than previously possible. His resistors were quickly incorporated into many products ranging from common household goods to complex military technology that are still used throughout the world today.

Read more!