| 摘要 |
PURPOSE:To obtain a frequency separation circuit with a simple constitution and low cost while the frequency selecting characteristic is attained by providing a parallel resonance circuit having a specific resonance frequency between the input sections of a differential amplifier in the frequency separation circuit. CONSTITUTION:When a multiplex signal is fed to an input terminal 2 and an input signal having frequency components f1, f2 to be detected is fed thereto, the impedance between the input terminals of the differential amplifier 23 shows the highest value at the resonance frequency f2. As a result, the attenuated frequency component of the frequency f2, that is, the frequency components including the frequency f1 as the major component is extracted. Further, since the component of the frequency f1 passes through a parallel resonance circuit 24, the frequency component having the frequency f2 mainly comprised of the difference component only between the signal in the fre quency f2 and the signal attenuated by the circuit 24 is extracted at the differential output of the differential amplifier 23 and the difference component of the frequency f1 is shut off. Thus, a specific component is extracted separately from an optional frequency component by the differential output side of the differential amplifier 23 and the input side of the differential amplifier 23 short-circuited by the parallel reso nance circuit 24. |
