Figure 8.25. This figure shows a 4 digit display consisting of 4 7-segment L E D displays. Above each display is a PNP transistor. The collector of each transistor is connected to the common anodes of the display below it. All the emitters are connected to VCC. Each base goes through its own current limiting resistor to the digit select inputs. The 7 segment anodes of all 4 digits are connected in parallel. Each of the 7 segment cathode lines connects through its own limiting resistor to the 7 segment driver lines. Only 11 control lines are needed to send numbers to the 4-digit, 7-segment display instead of 28 if each segment had to be driven separately. End verbal description.
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