JPS60261205A - Oscillating circuit - Google Patents

Abstract

PURPOSE:To execute a stable oscillation by a high frequency, by connecting one end of a circuit for tuning substantially with a higher order oscillation frequency of a vibrator, to an input terminal of an inversional amplifier, and connecting the other end to the ground potential through a capacity. CONSTITUTION:A crystal resonator 33 and a resistance R31 are inserted between an input terminal 35 and an output terminal 36 of an inversional amplifier 31 consisting of an insulating gate type FET, and capacities C33, C34 are connected between the input and output terminals 35, 36, respectively. Also, this circuit is provided with a parallel resonance circuit 34 consisting of an inductance L31 whose one end is connected to the input terminal 35 and whose other end is connected to the ground terminal through a DC obstructing capacity C32, and a capacity C31. As a result, the impedance of the amplifier 31 becomes maximum in the vicinity of a tuning frequency of the circuit 34 connected to the input. Therefore, when the tuning frequency of the circuit 34 is matched in advance to a higher order frequency of the resonator 33, an oscillation by a fundamental wave is not executed, and a higher order oscillation is executed in vicinity of the tuning frequency of the circuit 34.

Description

[Detailed description of the invention] (Technical field) The present invention relates to an oscillation circuit using piezoelectric elements.

(Prior Art) Conventionally, an oscillation circuit using, for example, a crystal resonator as a piezoelectric element uses a circuit shown in FIG.

This circuit is an insulated gate field effect transistor (hereinafter referred to as
It is called IGFET. ) A self-biasing resistor R11 is provided between the input and output of the inverting amplifier 11, and a crystal oscillator 13 is inserted between the input and output as a feedback circuit. crystal oscillator 1
3 load capacity ctt I C1! is added. Note that 12 is an inverting amplifier for output amplification. This circuit is self-biased by taking advantage of the high input impedance of the IGFET.

Therefore, the C1 inverting amplifier 11 is at the maximum profit point, as seen from the input/output characteristics shown in FIG. Also, self-bias resistance R
The 11O value only needs to be a value that satisfies the following relationship in the frequency region f where the input impedance is determined by the capacitance Ctt, and does not require delicate adjustment. Furthermore, although this circuit is an unadjusted oscillation circuit, it has good oscillation start characteristics and frequency maintenance characteristics. However, in order to oscillate in a higher-order vibration mode, oscillation cannot be achieved unless the circuit is designed to amplify higher-order vibrations to a greater extent than the fundamental wave.

In recent years, the frequency of integrated circuits operated at high frequencies has gradually increased, and it has become necessary to use crystal resonators with third-order overtones. In this case, the overtone oscillation circuit is constructed from a single transistor and various passive components, which increases the number of components and deteriorates reliability. Alternatively, there were disadvantages such as the need to adjust the bias circuit and disadvantageous manufacturing conditions.On the other hand, as shown in Figure 3, E CL (Em 1ter Coupled
A parallel resonant circuit is formed at the input of the crystal oscillation circuit using the Logic') circuit 21 with the inductance L21, and the crystal oscillator 23 is caused to oscillate by overtone by tuning to the required overtone oscillation frequency. (Patent pulse circuit technology encyclopedia, Ohmsha, 1st edition, published on May 20, 1972, p.
51). Note that C22 and C23 are capacitors, and R21
~R23 is a resistor, 22 is an output (ECL circuit for the buffer, -E is a power supply).

However, in this conventional circuit, a low bias resistor f(+, 1) is connected in parallel with the parallel resonant circuit, which lowers the Q of this resonant circuit, resulting in poor oscillation stability. there were.

(Object of the Invention) An object of the present invention is to provide an oscillation circuit that stably oscillates at a high frequency with a simple circuit configuration by eliminating the above-mentioned drawbacks.

(Structure of the Invention) The oscillation circuit of the present invention has a resonator and a resistance element connected between the input terminal and the output terminal of an inverting amplifier made of an insulated gate field effect transistor, and between the input terminal and the output terminal and the ground potential, respectively. In an oscillation circuit formed by connecting a capacitor, one end of a tuning circuit that is substantially tuned to the high-order oscillation frequency of the vibrator is connected to the input terminal of the inverting amplifier, and the other end is connected to a ground potential through the capacitor. Consists of connections.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 4 is a circuit diagram showing a first embodiment of the present invention.

This embodiment includes an inverting amplifier 31 made up of 1 GFET, and a crystal oscillator 3 inserted between its input terminal 35 and output terminal 36.
3 and a resistor R3, capacitors C33 and C34 connected between the input terminal 35 and the output terminal 36, and the ground terminal, respectively, and a capacitor C32 for direct current blocking with one end connected to the input terminal 35 and the other end. Inductance JJ connected to the ground end through
31 and a parallel resonant circuit 34 consisting of a capacitor C31. Note that 32 is an inverting amplifier for output amplification.

That is, this embodiment consists of adding a parallel resonant circuit 34 and a capacitor C32 to the conventional circuit shown in FIG.

As a result, the input impedance of this inverting amplifier 310 becomes maximum near the tuning frequency of the parallel resonant circuit 34 connected to the input. Therefore, if the tuning frequency of this parallel resonant circuit 34 is matched to the high-order frequency of the crystal oscillator 33, oscillation at the fundamental wave will not occur, but high-order oscillation will occur near the tuning frequency of the parallel resonant circuit 34. I will do it.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention.

In this embodiment, a filter circuit 37 consisting of an inductance L32 is used in place of the parallel resonant circuit 34 shown in FIG. This inductance L! 2 operates as a so-called no-pass filter that has low impedance near the fundamental wave and high impedance in higher-order modes. Now, the gain of the inverting amplifier 31 is 01, the attenuation rate of the feedback circuit (crystal oscillator 33) is β, and the attenuation rate of the filter circuit 37 attached to the input is γ.
Then, the total gain A is A = G By setting γ, it is possible to oscillate at a higher frequency without causing oscillation at the fundamental wave.

In addition, if the inverting amplifier 32 with the same input/output characteristics as the inverting amplifier 31 is connected in series, they have the same bias point, so DC coupling is possible, and when the oscillation amplitude is small, multi-stage amplification is possible, and it can be used in integrated circuits. A logical level can be ensured.

(Effects of the Invention) As described above in detail, according to the present invention, a high-order oscillation circuit can be obtained with a simple circuit configuration using the above configuration. The oscillation circuit of the present invention can be integrated except for the tuning circuit and the crystal oscillator, and there are no problems in terms of reliability or manufacturing, since the circuit constants hardly need to be adjusted.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a conventional crystal oscillation circuit;
The figure is a characteristic diagram of an inverting amplifier, FIG. 3 is a circuit diagram showing another example of a conventional crystal oscillation circuit, and FIGS. 4 and 5 are circuit diagrams showing the first and second embodiments of the present invention, respectively. It is. '31. '32...Inverting amplifier, 33...
...Crystal resonator, 34°°°...Parallel resonant circuit, 3
5...P input end, 36...Output end, 37...
...Filter circuit, C31 to C34...M
, L31 + L32...Inductance, 几31...Resistance. See 1 flash D Taku 2 flash 3 flash

Claims (1)

[Claims] In an oscillation circuit, a resonator and a resistance element are connected between the input terminal and the output terminal of an inverting amplifier composed of an insulated gate field effect transistor, and a capacitor is connected between the input terminal and the output terminal, respectively, and a ground potential. An oscillation circuit characterized in that one end of a tuning circuit substantially tuned to a higher-order oscillation frequency of the inverting amplifier is connected to the input end of the inverting amplifier and the other end is connected to a ground potential via a capacitor.