| 摘要 |
PURPOSE:To make the comparator, to which the triangular wave output and the sound signal are applied in the conventional circuit, needless to simplify the circuit constitution, by applying the sound signal into the triangular wave signal oscillating circuit and by shifting the level of the triangular wave signal to shape its waveform into a rectangular wave. CONSTITUTION:When sound signal (b) does not exist and the output voltage of sound amplifier 3 is zero volt, input voltage Vs of the noninversion terminal of comparator 8 has threshold voltages VS1=+VCCXR3/(R3+R4) and VS2=-VccX R3/(R3+R4), and capacitor C2 repeats charging and discharing with these voltages as the reference, and voltage VA of capacitor C2 becomes a triangular wave signal. This voltage VA has the waveform shaped by high-gain amplifier 11 and becomes pulse width modulation signal VO of duty 50%. Meanwhile, when sound signal (b) appears and its voltage is +Vb, voltage VS of the noninversion terminal of comparator 8 rises by +Vb, and triangular wave voltage VA is shifted as a whole by +Vb, and this voltage has the waveform shaped to obtain pulse width-modulated signal V0. |
