Posted on Mar 28, 2007 7759
Astable multivibrator using too many electronic devices, widely used in the pulse signal generating circuit, which works as 17-18 in FIG. From the figure shows, with A coupling
circuit between two transistors VT1 and VT2 to C2 and Rz way connected. The output VT2 VT1 sent out through the coupling circuit B (C, R,) form a positive feedback input, thus forming the oscillator circuit. Figure l in the transistor VT1 Sl replaced with a switch to VT1 VT2 omitted from the coupling circuit B (Ci, Rl), it now looks like Figure Figure (a) is a case of switching off sl, VT2 base from the power supply through R2 with a forward voltage, so that V-12 is turned on. At this time, the electrical path of the dashed line is current for charging the capacitor C2. Then the switch is closed sl t in FIG. (B) in Fig. Since the capacitor C2 is charged at this time, the voltage is cut o. So switch closure moment is equivalent to VT2 base plus negative pressure, so that VT2 end. Figure (b) in the direction of the broken line is the capacitance c7, the charge discharging direction to, then VT2 base voltage changes from negative to positive, VT2 then turned on again.