Alternative Base Switching

Chapter Alternative Base Switching

Complete Electronics Self Teaching Guide with Projects
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Complete Electronics Self Teaching Guide with Projects

  • CHAPTER 4 THE TRANSISTOR SWITCH166ANSWERSA. 200 mAB. 375 ΩC. 2 mAD. 37.5 kΩE. 16.7 μAF. 4.5 MΩG. Choose R2 = 1 MΩALTERNATIVE BASE SWITCHING28  In the examples of transistor switching, the actual switching was performed using a small mechanical switch placed in the base circuit of the first transistor. This switch has three terminals and switches from position A to position B. (This is a single-pole, double-throw switch.) This switch does not have a definite ON or OFF position, as does a simple ON-OFF switch.QUESTIONWhy couldn’t a simple ON-OFF switch with only two terminals have been used with these examples? ANSWERAn ON-OFF switch is either open or closed, and cannot switch between position A and position B, as shown earlier in Figure 4.19.29  If you connect R1, R2, and a switch together, as shown in Figure 4.20, you can use a simple ON-OFF switch with only two terminals. (This is a single-pole, single-throw switch.)Book Authorc04V107/04/2012 2:59 PM c04.indd 1667/4/2012 3:01:18 PM