Bandpass filter circuit
View Patent ↗A semiconductor integrated circuit device provided with an input terminal supplied with a reference frequency signal from outside of the device, a bandpass filter circuit coupled to the input terminal and outputting an internal reference frequency signal and a PLL circuit coupled to the bandpass filter circuit to receive the internal reference frequency signal. The input terminal is supplied with the reference frequency signal generated by a quartz oscillator or the like mounted on the exterior of the semiconductor integrated circuit device. In response to the signal supplied to the input terminal, the bandpass filter circuit restricts components in a bandwidth except for the frequency of the reference frequency signal, and thus supplies the reference signal to the PLL circuit. The PLL circuit operates by using the reference frequency signal as the reference signal.
1. A bandpass filter circuit comprising:
a serially-connected circuit comprising a first capacitance element and a first resistance element, a first end of the serially-connected circuit being coupled to an input terminal, and a second end thereof being coupled to an input terminal of a CMOS inverter circuit; and
a parallel-connected circuit comprising a second capacitance element and a second resistance element, a first end of the parallel-connected circuit being coupled to the input terminal of the CMOS inverter circuit, and a second end thereof being coupled to an output terminal of the CMOS inverter circuit.
2. The bandpass filter circuit according to claim 1 , further comprising an amplifier comprising the CMOS inverter circuit, wherein the CMOS inverter circuit comprises a first CMOS inverter circuit and the bandpass filter circuit further comprises:
a differential compensation circuit including a second CMOS inverter circuit for differential compensation, and a third resistance element having a resistance value equal to that of the second resistance element, a first end of the third resistance element being coupled to an input terminal of the second CMOS inverter circuit, and a second end of the third resistance element being coupled to an output terminal of the second CMOS inverter circuit; and
an operational amplifier, whose first differential input terminal is coupled to an output terminal of the bandpass filter circuit, whose second differential input terminal is coupled to an output terminal of a differential input terminal of the differential compensation circuit.