555 Voltage-controlled Oscillator Circuit with its Duty Cycle Controlled by Vc Terminal

Published:2011/8/1 23:41:00 Author:Zoey | Keyword: 555 Voltage-controlled Oscillator Circuit, duty cycle , Vc terminal | From:SeekIC

Circuit of the multi-vibratorhas beenshown in thepicture 3-20, oscillator frequency and duty cycle of the vibratorare adjusted according to the level on pin 5, which is controlled by 555 controlling terminal Vc. A 555, R1, R2 and C1 together constitute an astable multi-vibrator. The controlling terminal can change the level it controlledthrough RP1,it also controls the voltage of comparator A1’s reverse terminal in the chip, adjusts comparator’s baseline voltage so as to change the turnover level of RS trigger and time constant of charge and discharge loop. As illustrated in picture(b), we can take advantage of the oscillation pulse , which is voltage-controlled, to adjust the voltage of duty cycle without changing oscillation frequency, or to transfer the pulse width, pulse position as well as the voltage. Concrete operation can be seen in 5-26, 5-27 and 5-31,etc in chapter 5.



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