| 摘要 |
PURPOSE:To achieve stable oscillation even at a low voltage, by inputting a charging/discharge voltage to a parallel circuit of a resistor and a capacitor at the input side of a Schmitt trigger circuit, through the on/off control of a transistor (TR) feeding the output of a Schmitt trigger circuit back to the input. CONSTITUTION:An output of a Schmitt trigger circuit 1 is fed back to the input side via a TRQ3. When an input Vin is at high level, a TRQ1 is conductive. A TRQ2 is nonconductive and a current I1 flows to an emitter resistor RE to produce a voltage drop of RE.I1. To turn off the TRQ1, the input Vin should be smaller than VBE1+REI1. When the TRQ1 is nonconductive, a voltage drop of RE(I1+I2) is produced at an emitter resistor RE, where I2 is the collector current of the TRQ2. To turn on the TRQ1, the input Vin should be higher than{VBE1+RE(I1+I2)}. Thus, two stable points of VBE1+REI1 and VBE1+ RE(I1+I2) are produced in the input Vin, and oscillation is made with transit between the two stable points. |
