| 摘要 |
PURPOSE:To make a sine wave oscillation output highly stable against temperature variation and to suppress variation in oscillation frequency by feeding the output of an error amplifying circuit back to the input terminal of a sine wave oscillation circuit. CONSTITUTION:When the oscillation output VOSC of an output driver circuit 2 is inputted to a point (a) as a sine wave having an amplitude ei through a nomitor line 8, a negative half-cycle wave having an amplitude ed appears at a point (b), and the absolute value output of the amplitude ea is further obtained at a point (c). A capacitor C30, on the other hand, is connected to the resistance R34 of an adding circuit 34 to constitute an LPF together with a resistance R35 connected to an output terminal and the output ea is obtained as a DC mean value, so that variation in output VOSC with temperature is detected as variation in the DC means value ea of an absolute value circuit 3. The operational amplifier 41 of the error amplifying circuit 4 compares the output ea with the reference voltage Vref of a high-precision, high-stability reference voltage source to detect an error, which is amplified and fed back to the gate G of the FETQ1 of a Wien bridge type oscillation circuit 1. |
