| 摘要 |
PROBLEM TO BE SOLVED: To eliminate such a fault as stoppage of oscillatory operation after oscillation, prolongation of oscillation settling time, failure of oscillation during start, or the like, due to variation in operational conditions of an oscillator such as fall of power supply voltage or temperature rise. SOLUTION: An inversion amplifier Inv_Amp which can connect an oscillator between the input/output terminals includes a PMOSMp1 and an NMOSMn1. A plurality of D/A converters D/Ap_1, ..., D/Ap_n, D/An_1, ..., D/An_n including a resistor and an MOS switch are connected between the source of the Mp1 and the power supply voltage Vcc or between the source of the Mn1 and the ground GND so that output impedance is varied in response to a digital input signal. Variation in operational conditions of a variable gain oscillator VG_OSC is detected by an A/D conversion unit 102 and total output impedance of the plurality of D/A converters is varied gradually. COPYRIGHT: (C)2008,JPO&INPIT
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