LED 2N2907A ve- (a) For use when LSTTL drives an LED (b) For use when a logic high is needed to drive an LED FIGURE 83.7 LED interfacing for(a)low-power transistor-transistor logic,(b)logic high drive, and(c)CMOS ( Source: M. Forbes and BB Brey, Digital Electronics, Indianapolis: Bobbs-Merrill, 1985, P. 242. With permission. +Vcc NATIONAL L-- LED2 立=LED1 BAR GRAPH DISPLAY POSITION INDICATOR DISPLAY FIGURE 83.8 Operational amplifiers or voltage comparators used to decode an analog signal into a bar graph or position dicator display.( Source: S. Gage et al, Optoelectronics/Fiber-Optics Applications Manual, 2nd ed, New York: Hewlett Packard/McGraw-Hill, 1981, P. 23.3. With permission. used to indicate signal level on audio equipment, with a modification of the position indicator seen in Fig. 83.8 to guide fine tuning. Matrix LED arrays can be used for flexible, high-density panel displays [Fig 83.9(a)] and are conventionally controlled by row or column strobing[ Fig 83.9(b)] controlled by a microprocessor interface. Multiple LEDs are commonly packaged together in a single integrated device, organized in one of the standard display fonts Fig 83. 10(a)l, with decoding often included within the package [Fig. 83. 10(b)]. The 7-segment e 2000 by CRC Press LLC© 2000 by CRC Press LLC used to indicate signal level on audio equipment, with a modification of the position indicator seen in Fig. 83.8 to guide fine tuning. Matrix LED arrays can be used for flexible, high-density panel displays [Fig. 83.9(a)] and are conventionally controlled by row or column strobing [Fig. 83.9(b)] controlled by a microprocessor interface. Multiple LEDs are commonly packaged together in a single integrated device, organized in one of the standard display fonts [Fig. 83.10(a)], with decoding often included within the package [Fig. 83.10(b)]. The 7-segment FIGURE 83.7 LED interfacing for (a) low-power transistor-transistor logic, (b) logic high drive, and (c) CMOS. (Source: M. Forbes and B.B. Brey, Digital Electronics, Indianapolis: Bobbs-Merrill, 1985, p. 242. With permission.) FIGURE 83.8 Operational amplifiers or voltage comparators used to decode an analog signal into a bar graph or position indicator display. (Source: S. Gage et al., Optoelectronics/Fiber-Optics Applications Manual, 2nd ed., New York: Hewlett￾Packard/McGraw-Hill, 1981, p. 23.3. With permission.)