Published:2011/7/5 0:10:00 Author:Zoey | Keyword: 555 Voltage-controlled Oscillator, Adjustable Duty Cycle Period | From:SeekIC
The voltage-controlled oscillation circuit has been shown in picture3-19. 555, R1, R2, C1~C3 and VT1 constitute a voltage-controlled multi-vibrator. As a voltage-controlled resistance, JFET can change the impedance between D/S. The coupling capacitance of D and S is used to eliminate the effect of other direct voltage on JFET. Timing capacitance of C1 and C2 should be selected as large as 10 times of C3.
Advantage of this circuit is that, an adjustable and changeable resistance can be formed by changing VGS, so as to obtain a large duty cycle and a changeable period.
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