| 摘要 |
<p>An FM signal demodulation circuit capable of demodulating higher frequencies while maintaining linearity in the input and output signals. A first differential amplifier circuit (DA1) is supplied with an FM signal of one phase and a constant voltage (VBB), while a second differential amplifier circuit (DA2) is supplied with an FM signal of the opposite phase and a constant voltage (VBB). The two differential amplifier circuit (DA1, DA2) have their respective constant-current circuit (13, 17) which are coupled together via a capacitor (C). A frequency-demodulated signal is obtained by smoothing a pulse output signal (Vc) of a predetermined width that is obtained by comparing the output signal of the differential amplifier circuit (DA2) with a reference voltage (Vref). In the frequency demodulation circuit, a current (I2) of the second constant-current source (17) is set to be greater than a current (I1) of the first constant-current source (13), whereby the electric charge stored in the capacitor (C) is quickly recovered to increase the frequency that can be demodulated.</p> |
