| 摘要 |
PROBLEM TO BE SOLVED: To provide a voltage controlled oscillation circuit which can secure a gain even at low power voltage and which is suitable for reducing power voltage. SOLUTION: A lag-lead filter 21 extracting a low frequency component contained in an input signal, a series resonance amplifier outputting a resonance signal oscillated with the resonance frequency of a crystal oscillator in accordance with the output signal of the lag-lead filter 21, a sub-amplifier 23 amplifying the resonance signal and a phase shift circuit 24 giving phase shift quantity in accordance with a control signal to the output signal of the sub-amplifier 23 are installed. The output signal of the phase shift circuit 24 is fed back to the lag-lead filter 21 and the voltage controlled oscillation circuit of loop structure is formed. In an operation with low power voltage, the gain of the sub-amplifier 23 is set in accordance with the drop of the gain of the phase shift circuit and the drop of the gain of the phase shift circuit 24 is compensated, the loop gain is kept to be not less than a constant reference value and an oscillation operation can normally be maintained even a low power voltage.
|
