SU1598103A1 - Quartz oscillator - Google Patents

Abstract

This invention relates to radio engineering and can be used as a source of highly stable electrical oscillations. The purpose of the invention is to increase the reliability of excitation and increase the stability of the frequency of output oscillations. The drawing shows a circuit diagram of a crystal oscillator, according to which it contains the first and second transistors 1.2, the first, second and third resistors 3-5, a quartz resonator (CR) 6, the first, second and third capacitors 7-9. When the crystal oscillator 6 is turned on, the gain of the cascade performed on the second transistor 2 at the series resonance frequency of CD 6 is greater than one and, therefore, the amplitude balance condition in the crystal oscillator is provided. Tuning to mechanical harmonics KP 6 is performed by selecting the capacitance of the first capacitor 7. At frequencies different from the frequency of the series resonance KP 6, the complex resistances of the collector circuit and the emitter of the second transistor 2 are the same in a wide frequency range, parasitic generation at high frequencies is prevented. 1 il.

Description

The invention relates to radio engineering and can be used as a source of highly stable electrical oscillations.

The purpose of the invention is to increase the reliability of excitation and increase the stability of the frequency of the output oscillations.

The drawing shows a circuit diagram of a crystal oscillator.

The crystal oscillator contains the first 1 and second 2 transistors, the first 3, the second 4 and the third 5 resistors, a quartz resonator 6, the first 7, the second 8 and the third 9 capacitors.

A crystal oscillator operates as follows.

The cascade on the first transistor 1 is an emitter follower with a tuned emitter circuit, while the inductive component of the output resistance of the cascade and the capacitance of the first capacitor 7 is a series circuit tuned to the operating frequency.

At the resonance frequency, the current through the first transistor 1 lags behind the input voltage by an angle close to ktg / 2, and the voltage at the first capacitor 7 lags behind the current through it also by an angle close to π / 2. Therefore, the phase shift of the cascade performed on the first transistor 1 between the input and output voltage is tg at the resonance frequency of the emitter circuit, and the transfer coefficient is slightly less than unity.

The cascade on the second transistor 2 is made with sequential current feedback due to the inclusion of the third resistor 5 in its emitter circuit. When choosing the resistance values of the second 4 and third 5 resistors equal to each other, the cascade gain on the second transistor 2 is unity, and the phase shift equal to mf.

Thus, in the absence of a quartz resonator 6, the condition of the balance of amplitudes in the quartz oscillator is not fulfilled, since the total gain in the feedback circuit is less than unity.

When the quartz resonator 6 is turned on in parallel with the third resistor 5, the gain of the cascade performed on the second transistor 2 at the frequency of the series resonance of the quartz resonator 6 is greater than unity and, therefore, the amplitude balance condition in the quartz oscillator is ensured.

The tuning of the crystal oscillator to the mechanical harmonics of the crystal resonator 6 is carried out by selecting the capacitance of the first capacitor 7.

To prevent spurious generation at high frequencies, a second capacitor 8 can be connected in parallel with the second resistor (at low frequencies, the second capacitor 8 can be excluded from the crystal oscillator), the capacitance of which is equal to the static capacitance of the crystal resonator 6. At the same time, at frequencies other than the frequency of the series resonance quartz resonator 6, the complex resistances of the collector and emitter circuits of the second transistor 2 are equal to each other in a wide frequency range.

The third capacitor 9 is an interlock, and the first resistor 3 determines the direct current mode of the first transistor 1.

Claims (1)

Claim A quartz generator containing a first transistor, the emitter of which is connected in parallel to the first resistor and the first capacitor is connected to a common bus, the second transistor, the collector of which is connected via a second resistor to the power bus, and the emitter of which is connected to a common bus through a third resistor, the third capacitor the capacitor, the first output of which is connected to the common bus, a quartz resonator, while the base of the first transistor is connected to the collector of the second transistor, characterized in that, in order to increase excitation and stability of the output oscillation frequency, a crystal is connected between the emitter of the second transistor and the common bus, the second capacitor is connected between the collector of the second transistor and the power supply, the second output of the third capacitor and the collector of the first transistor are connected to the power supply of the first transistor transistor.