| 摘要 |
PROBLEM TO BE SOLVED: To stably and effectively obtain FM modulation output which becomes always constant ratio to a center frequency without depending on diffusion irregularity and temperature fluctuation of a semiconductor integrated circuit. SOLUTION: A multivibrator 200 whose oscillation frequency is changed by a control current, and a voltage current converting part 300 which converts a signal voltage Vsig to be modulated to a control current, are installed. The voltage current converting part 300 is provided with mutual conductance converters 7, 8, current sources I1-I4, and a current source I5 for defining the center frequency fo of a voltage-controlled oscillator. Constitution is so performed that the sum of currents of a current Iadj1 for adjusting the center frequency of the voltage-controlled oscillator, a current Isig for defining modulation factor of the voltage-controlled oscillator and the current source I5 is made a control current Im of the voltage-controlled oscillator. The power sources I1, I3 are constituted to depend on a diffusion resistance value, and the power sources I2, I4, I5 are constituted to depend on an external resistance value.
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