JPH0332090Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a piezoelectric oscillator that consumes low current and oscillates at a stable frequency.

[Prior Art] Among piezoelectric vibrators, crystal resonators are widely used as clock sources and signal sources in industrial equipment, communication equipment, and digital equipment. And recently,
There is a demand for smaller size and lower current consumption. However, in conventional crystal oscillators, load fluctuations occur when the oscillation section that generates oscillation from the crystal oscillator is connected to the next stage. Therefore, a buffer section was required to prevent the effects of load fluctuations. However, this buffer section consumes power supply current, making it an impediment to miniaturization and lower power consumption. For example, even if the oscillation section of a crystal oscillator consumes 2 mA, the buffer section will consume more than 3 mA of current. Therefore, in order to keep both parts below 5 mA, it was impossible to make it below 3 mA even if constants were selected.

Therefore, a transistor-directly connected circuit was announced in Japanese Patent Application Laid-Open No. 19753/1975, which realized low current.

FIG. 2 shows a circuit of a conventional piezoelectric oscillator, in which the oscillating section and the transistor of the buffer section are directly connected. In such a circuit, it is necessary to stabilize the bias circuit. That is, the bias tends to fluctuate depending on the temperature, and the oscillation frequency and oscillation output deteriorate unless diodes D1 and D2 are inserted for stabilization.

[Problems to be solved by the invention] In order to solve these problems, the oscillation frequency can be increased without stabilizing the bias by reducing the current consumption and creating a circuit with fewer parts for miniaturization. A circuit with stable output was considered.

[Configuration of the present invention] The configuration of the present invention is that in a piezoelectric oscillation circuit in which an oscillation transistor and a buffer transistor of an oscillation circuit using a piezoelectric vibrator are directly connected, a power supply is transmitted from a power source through a load element connected to a buffer transistor. This is a piezoelectric oscillation circuit that supplies base bias for buffer and oscillation transistors.

[Operation and Examples] FIG. 1 is a circuit diagram showing an example of the present invention. A crystal resonator X is connected to the transistor TR1, forming an oscillation section. capacitor C2,
C3 is a capacitor for oscillation. The transistor TR2 is a transistor in the buffer section, and is connected in series with the oscillation transistor TR1. The buffer transistor TR2 has a common base, and the signal output is from the transistor.
It is output from the collector of TR2 to output terminal 1 through capacitor C5. Transistor TR1
The bias of TR2 and TR2 are connected from the power supply terminal 2 to the load resistor R4, which is connected to the collector of the transistor TR2, and from the collector thereof to the respective bases through resistors R2 and R3. Conventionally, bias has been supplied by a so-called bleeder resistor, in which two resistors are connected in series between the power supply and ground, but in the present invention, the bias is drawn out from the power supply after passing through the load element. If the collector of the buffer transistor and the base of the buffer transistor are connected via a resistor, and the collector of the buffer transistor and the base of the oscillation transistor are connected via a resistor, the base of each transistor It's biased. The current flowing through this resistor corresponds to the collector current of the buffer transistor. This is because DC feedback is applied to each transistor, and as with AGC, the collector current of the buffer transistor is constant, so the current flowing through each transistor is constant, which stabilizes the DC operation of the circuit and stabilizes the oscillation frequency.

As a result of this configuration, a diode for bias stabilization, which was always necessary in the conventional circuit, is no longer necessary, and a stable output can be obtained even without the diode. Of course, if it is stabilized with a diode or the like, even more remarkable effects can be obtained. For example, if a constant current diode is connected in series with the resistor R2, stability will be improved compared to the conventional circuit.

In this embodiment, an example is shown in which the resistor R4 is connected as the load of the transistor TR2, but the effect is the same even if it is an inductance.

Although a crystal resonator is used as the piezoelectric material in the embodiment, other materials such as lithium tantalate, piezoelectric ceramic, etc. may be used in addition to the crystal resonator.

[Effects of the present invention] In conventional direct-coupled circuits, the output frequency and output level could not be stabilized unless the bias was stabilized with a diode, etc. However, with the present invention, the output frequency and output level could not be stabilized without stabilizing the bias. Stable frequency and output can now be obtained. Additionally, the number of components is reduced compared to conventional circuits, making it possible to downsize.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a piezoelectric oscillator according to the present invention,
FIG. 2 is a diagram of a conventional piezoelectric oscillation circuit. TR1, TR2...transistor, R4...load element, X...crystal oscillator.

Claims (1)

[Scope of utility model registration request] In a piezoelectric oscillation circuit in which the collector of an oscillation transistor of an oscillation circuit using a piezoelectric vibrator is connected to the emitter of a buffer transistor, a load element is connected between a power supply and the collector of the buffer transistor, and the buffer transistor is connected to the collector of the buffer transistor. A piezoelectric oscillation circuit characterized in that the collector of the piezoelectric oscillator is connected to the bases of buffer and oscillation transistors via resistors, respectively.