Semiconductors are now being used extensively in commercial products, industry, and all
branches of the armed services.
1-17. Semiconductor devices can and do perform all the conventional functions of
rectification, amplification, oscillation, timing, switching, and sensing. These devices
perform the same basic functions as the electron tube but perform more efficiently,
economically, and for a longer period of time. Therefore, it should be no surprise to see
these devices used in place of electron tubes. Keeping this in mind, we see that it is only
natural and logical to compare semiconductor devices with electron tubes.
1-18. Semiconductor devices are physically much smaller than tubes. Figure 1-1 shows
some commonly used tube sizes alongside semiconductor devices of similar capabilities.
The reduction in size can be as great as 100:1 by weight and 1,000:1 by volume. It is easy
to see that size reduction favors the semiconductor device. Therefore, whenever
miniaturization is required or is convenient, transistors are favored over tubes. However,
that the extent of practical size reduction is a big factor; many other things must be
considered. For example, miniature electron tubes may be preferred in certain applications
to transistors, thereby keeping size reduction a competitive area.
Figure 1-1. Size Comparisons of Electron Tubes and Semiconductors
1-19. For low-power applications, where efficiency is a significant factor,
semiconductors have a decided advantage. This is true mainly because semiconductor
devices perform very well with an extremely small amount of power. They also require no
filaments or heaters, as in the case of the electron tube. For example, a computer operating
with over 4,000 solid state devices may require no more than 20 watts of power. However,
the same number of tubes would require several kilowatts of power.
1-20. For high-power applications, tubes have a decided advantage. The high-power
electron tube has no equivalent in any semiconductor device. This is because a tube can be
designed to operate with over a thousand volts applied to its plate while the maximum
23 June 2005