Oscillator circuits

There is provided an oscillator circuit in which an oscillation permitting signal (EN) sets an oscillator section (5) in an oscillation-operable state, whereby a controller section (4) starts operation. The controller section (4) that has started its operation changes an oscillation-frequency control signal (VR) value corresponding to a predetermined oscillation frequency so as to set an oscillation frequency at an oscillator section (5). Further on, the oscillator section (5) outputs an oscillation signal (VOSC) in response to a detection signal (MON) that is outputted after a detector section (1) compares a signal inputted therein with a predetermined signal value and detects that the inputted signal reaches a predetermined signal value. Thereby, a transient state of an oscillation-frequency control signal (VR) can be detected. That is, there can be avoided an output of an unstable oscillation signal due to a transient oscillation-frequency control signal (VR). Such an oscillator circuit is capable of obtaining stable frequency by avoiding output having unstable frequency that is likely to occur to an operation/stop-control-feasible type oscillator circuit when oscillation begins.