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555 Symmetrical wave Multi-vibrator

2015-02-05 11:40  
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555 Symmetrical wave Multi-vibrator
555 Symmetrical wave Multi-vibrator
555 Symmetrical wave Multi-vibrator
555 Symmetrical wave Multi-vibrator
As shown in the figure 3-18, this multi-vibrator has added a positive bias triode VT1. With the positive bias effect of R2, VT1 can be fully conducted; but as soon as C1 discharges, it will not be conducted. As the switch pipe VT1 and Germanium diode is in the state of conduction, the positive conduction resistance is weak, so it has little effect on charge and discharge time constant. The charge time, discharge time, oscillation period and duty cycle can be calculated by following formula: T1=0.693(R1+RP1)•C1 T2=0.693(R1+RP1)•C1 T=0.693(2R1+2RP1)•C1 D=T2/D=50% Another merit of this circuit is, the load change has little effect on voltage output, duty cycle and oscillation frequency. Figure 3-18 Multi-vibrator that can output symmetrical wave Figure 3-19 Voltage-controlled oscillator with an adjustable duty cycle period