JPH03220906A - Crystal oscillator - Google Patents

Abstract

PURPOSE:To obtain a stable sinusoidal crystal current waveform by interposing a resistor to limit a crystal current flowing to a crystal resonator in series with an output of an inverter. CONSTITUTION:A resistor 16 to limit a crystal current flowing to a crystal vibrator 12 is interposed to an output of an inverter 11. Even when a high speed inverter is used for the inverter 11, a current flowing to the crystal resonator 12 is limited by a resistor 16 and a sinusoidal crystal current without distortion including no harmonic component is obtained. Thus, a stable sinusoidal crystal current is obtained and a crystal oscillator suitable for temperature compensation especially is obtained without a jump in the temperature characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a crystal oscillator that operates stably and can obtain a sinusoidal output waveform.

(Technical background of the invention and its problems) Conventionally, a crystal oscillation circuit using an inverter as shown in FIG. 4 has been widely used. In other words, recently, invar
In particular, the performance of semiconductor elements has been significantly improved, and devices capable of high-speed operation are becoming widespread.

However, if a crystal oscillator circuit as shown in FIG. 4 is manufactured using such a device capable of high-speed operation, the drive level for the crystal resonator is too high and an excessive crystal current flows. For this reason, there is a problem in that, for example, a jump phenomenon occurs in which the characteristics jump.

(Object of the Invention) The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a crystal oscillator that can obtain a stable sinusoidal crystal current waveform and has no jump in temperature characteristics. It is.

(Summary of the Invention) The present invention is characterized in that, in an oscillation circuit in which a crystal resonator is connected between the input and output of an inverter, a resistor is inserted in series at the output of the inverter to limit the crystal current flowing through the crystal resonator. It is something.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the block diagram shown in FIG.

In the figure, 11 is an inverter, and a crystal oscillator 12 and a feedback resistor 13 are connected between this human power and the output. The value of this feedback resistor 13 varies depending on the frequency of the crystal resonator 12, but is generally several hundred ohms to several Mohms. Then, the human power and output of the inverter 11 are connected to capacitors 14 and 15, respectively.
It is grounded. The value of this capacitor 14.15 is also several P
F to a hundred and several tens of PF. A resistor 16 is inserted into the output of the inverter 11 to limit the crystal current flowing through the crystal resonator 12. The value of this resistor 16 is from several hundred Ω to several tens of Ω, and adjusts the crystal current flowing through the crystal resonator 12 to an appropriate value.

With such a configuration, even if a high-speed operation type is used as the inverter 11, the current flowing through the crystal resonator 12 can be controlled by the resistor 16.
For example, as shown in FIG. 2, a sinusoidal crystal current waveform containing no harmonic components and no distortion can be obtained.

Therefore, there is no jump or the like in the temperature characteristics, and good characteristics can be obtained especially in a temperature compensated oscillator that compensates to maintain the frequency at a constant value in response to temperature changes.

In addition, as in the above embodiment, a resistor 16 is connected to the output of the inverter.
By inserting , it is possible to move the region exhibiting negative resistance to a lower frequency region, as shown in the graph showing the relationship between frequency and negative resistance value shown in FIG.

That is, in FIG. 3, curve A is the characteristic of negative resistance in a conventional oscillation circuit as shown in FIG. Curve B shows the characteristics when a resistor 16 with a relatively small resistance value is inserted, and curve C shows the characteristics when a resistor 16 with a relatively large resistance value is inserted. i.e. resistance 1
By inserting a relatively large resistance value as 6 into the output of the inverter 11, the oscillation circuit suppresses the negative resistance at high frequencies, thereby suppressing overtone resonance and ensuring the oscillation output at the fundamental frequency. can be obtained.

Note that the present invention is not limited to the above embodiments,
For example, in the above embodiment, the capacitors 14 and 15 were explained as fixed capacitors, but it is also possible to use one or both of them as voltage-capacitance conversion elements to control the applied voltage and perform temperature compensation. Of course.

(Effects of the Invention) As detailed above, according to the present invention, it is possible to provide a crystal oscillator which can obtain a stable sinusoidal crystal current waveform and is particularly suitable for temperature compensation without jumps in temperature characteristics.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing the crystal current waveform of the above embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between frequency and negative resistance of the present invention. 4 is a block diagram showing an example of a conventional crystal oscillator, and FIG. 5 is a diagram showing an example of a crystal current waveform of the conventional crystal oscillator. 1 l ・ l 2 ・ l 3 ・ 14, l 6 ・ ... Inverter ... Crystal oscillator ... Feedback resistor 15, Capacitor ... Resistor': A212] 3rd Leap Collection 4th Figure 5

Claims (1)

[Scope of Claims] An oscillation circuit in which a crystal resonator is connected between the input and output of an inverter, characterized in that a resistor is inserted in series to the output of the inverter to limit the crystal current flowing through the crystal resonator. crystal oscillator.