The previous three chapters have described various optoelectronic display circuits based on simple LEDs. The present chapter continues the display theme by looking at 7-segment alphanumeric displays and at a variety of associated display-driver devices and circuitry.
A very common requirement in modern electronics is that of displaying alphanumeric characters. Digital watches, pocket calculators, and digital multimeters and frequency meters are all examples of devices that use such displays. The best-known type of alphanumeric indicator is the 7-segment display, which comprises seven independently accessible photoelectric segments (such as LEDs or liquid crystals, or gas-discharge or fluorescent elements, ...