| 摘要 |
PROBLEM TO BE SOLVED: To make output voltage linearly proportional to power supply voltage by applying operation voltage to a drive circuit from a power supply and controlling a drive level corresponding to power supply voltage. SOLUTION: In a drive circuit 21, a current amplifier 26 is connected to a drive value electrode 16 and a level detector 29 converts the output signal sine wave peak of an amplifier 26 to an equivalent RMS value to compare the same with a reference current. The difference between them is amplified by a loop amplifier 31 to control the gain of an automatic gain control amplifier 28 to be outputted to a drive high electrode 17. By this constitution, vibration is applied to a two-terminal tuning fork 11 to form a signal which is, in turn, inputted to the charge amplifier 33 of a pickup circuit 22 from a pickup low electrode 18 and a high electrode 19 through a resistor 37. This signal is demodulated by a synchronous demodulator 34 according to the signal from the amplifier 26 and filtered by a low pass filter 36 to be transmitted to an output terminal 39. At this time, operation voltage is applied to the circuit 21 from a power supply as reference voltage and the gain of an amplifier 28 is adjusted according to the change of the operation voltage to make a drive signal and an output signal proportional to the operation voltage. |
