| 摘要 |
PURPOSE:To improve the linearity of a voltage versus frequency conversion characteristic by providing a negative feedback circuit applying negative feedback of a demodulation signal outputted from a demodulation-means to an input circuit of an analog signal while including the demodulation means corresponding to a part of input of a pulse frequency modulation signal outputted from a pulse frequency modulator. CONSTITUTION:An analog signal such as a video signal inputted from a terminal 51 is amplified by a broad band amplifier 1 and the amplified signal is inputted to a pulse frequency modulator 2. The analog signal is subjected to pulse frequency modulation at the pulse frequency modulator 2 and the pulse frequency modulation signal is outputted via a terminal 52. Part of the pulse frequency modulation signal is inputted to a low pass filter 3 forming a negative feedback circuit and demodulated, the demodulation signal is amplified to a prescribed level by a broad band amplifier 4 and fed back negatively to the amplifier 4. The distortion in the voltage versus frequency conversion characteristic shown in 102 in figure caused in the pulse frequency modulator 2 is remarkably improved and the votlage versus frequency conversion characteristic with excellent linearity shown in 101 in the figure is realized. |
