Integrated circuit for transceiver device with means for suppressing superimposed noise and for generating a more accurate output signal

A filter circuit for an input signal having two logical levels, the filter circuit comprising:

• a current mirror circuit comprised of a first and second transistors having their control electrodes connected to each other, with the voltage of the joined control electrodes varying in response to the variation in level of the input signal;
• a first constant current circuit connected to the first transistor;
• a filtering capacitor;
• a second constant current circuit which produces a constant current which is 1/N (N>1) of a constant current flowing through the second transistor which is connected in series to the filtering capacitor;
• an offset voltage generation circuit which is connected between one terminal of the filtering capacitor on which the constant current from the second constant current circuit flows in and the second transistor, and adapted to produce a prescribed offset voltage;
• and
• a logical bi-leveling circuit for producing an output signal having two logical levels based on the voltage between the terminals of the filtering capacitor.

A trapezoidal wave signal generation circuit comprising:

• a capacitor having one terminal connected to a first power supply line and another terminal adapted to generate a trapezoidal wave signal;
• a first current output circuit connected between a second power supply line and the another terminal of the capacitor, wherein the first current output circuit is for conducting a charge current to the capacitor;
• a second current output circuit for conducting a discharge current that is twice the charge current, wherein the second current output circuit conducts the discharge current from the capacitor when a waveform control signal is at a first level, and halts the current conduction when the waveform control signal is at a second level;
• a first threshold voltage generation circuit for producing a plurality of threshold voltages by basing a reference on a voltage of the first power supply line;
• a second threshold voltage generation circuit for producing a plurality of threshold voltages by basing another reference on a voltage of the second power supply line;
• and
• a current control circuit for controlling the first and second current output circuits based on a comparison of the voltage between the terminals of the capacitor with the threshold voltages such that a voltage difference between the capacitor terminal voltage and the voltage of the first or second power supply line corresponds to the charge and discharge currents of the capacitor.