| 摘要 |
PURPOSE:To improve the stability of an output level and to simplify a circuit by detecting and controlling the level of a sine wave extracted from a rectangular wave. CONSTITUTION:An input signal composed of a rectangular wave is passed through amplifying circuit AMP and filter BPF to extract the sine wave output. Part of this output is converted by diode D1 and capacitor C into the DC voltage that corresponds to the output level. Then, differential amplifying circuit D-AMP amplifies the difference between the DC voltage and reference voltage Vs and subtracts the amplified voltage from reference voltage Vs to output the difference. Thus, the output rectangular wave of AMP is amplitude-limited according to the output voltage of D-AMP. An automatic gain adjustment loop is formed as mentioned above, so the level of the sine wave output from BPF is held constant at any time even if the load fluctuates. Further, none of elements such as FET and a thermistor is required, simplifying the circuit. |
