Abstract: The present invention is directed to reduce fluctuations in modulation frequency of a VCO caused by a temperature change in a semiconductor integrated circuit for use in a radio communication system of a frequency hopping method performing modulation by controlling the VCO of an LC oscillation type in accordance with transmission data in an open loop by using the VCO. In a semiconductor integrated circuit of a frequency hopping method performing modulation by directly controlling an LC oscillation type VCO on the basis of transmission data and transmitting data while switching a carrier frequency, a temperature characteristic correcting circuit is provided which give a negative temperature characteristic to a reference current value of a circuit (such as a DA converter) for generating a control voltage of the VCO so that a modulation-side control input voltage having a positive temperature characteristic and controlling the VCO comes to have a negative temperature characteristic.

Abstract: The present invention is directed to reduce fluctuations in modulation frequency of a VCO caused by a temperature change in a semiconductor integrated circuit for use in a radio communication system of a frequency hopping method performing modulation by controlling the VCO of an LC oscillation type in accordance with transmission data in an open loop by using the VCO. In a semiconductor integrated circuit of a frequency hopping method performing modulation by directly controlling an LC oscillation type VCO on the basis of transmission data and transmitting data while switching a carrier frequency, a temperature characteristic correcting circuit is provided which give a negative temperature characteristic to a reference current value of a circuit (such as a DA converter) for generating a control voltage of the VCO so that a modulation-side control input voltage having a positive temperature characteristic and controlling the VCO comes to have a negative temperature characteristic.

Abstract: A voltage-controlled filter circuit has a cutoff frequency directly proportional to a ratio of two current values. The filter circuit comprises a variable conductance circuit having two bipolar junction input transistors supplied with an input voltage signal at the bases thereof and a first variable current source at each emitter thereof. The collectors supply the bases of a pair of differential transistors. A second variable current supply is coupled to common emitters of the pair of differential transistors. Externally supplied control signals set the two current values of the variable current sources. The filter circuit may be manufactured as a semiconductor integrated circuit device for signal processing for use in processing a recorded signal read from a recording medium. The recorded signal is supplied to a semiconductor integrated circuit for signal processing to remove unwanted signal and noise components.