RU2319285C1 - Crystal oscillator - Google Patents

Abstract

FIELD: radio engineering; master oscillators for radio-transmitting equipment.

SUBSTANCE: proposed crystal oscillator has two transistors of which one incorporates common-base stage and other one, common-collector stage; oscillatory circuit; quartz resonator; interlocking capacitor; two isolating capacitors; two resistors; choke coil; two resistive voltage dividers; capacitor.

EFFECT: enhanced operating stability of common-collector stage, extended operating temperature range.

1 cl, 1 dwg

Description

The invention relates to the field of radio engineering and can be used in the construction of master generators of radio transmitting devices.

Known crystal oscillator (KG), containing two stages on transistors with a common base (OB) and with a common collector (OK), resistors, a voltage divider of the transistor, a quartz resonator connected between the emitters of transistors, a blocking capacitor (AS USSR No. 432655 , publ. 06/15/1974, Н03В 5/32). However, this crystal oscillator does not provide sufficient stability of the cascade with a common collector.

As the closest analogue, a quartz generator, known in the literature as the Butler circuit (A.F. Plonsky et al., "Transistor meter wave oscillators stabilized at the mechanical harmonics of quartz," published by Svyaz, Moscow, 1969), can be taken. , p. 125-126), containing two amplification stages on transistors, one of which is made with a common base (OB), and the other is an emitter follower - with a common collector (OK), a parallel LC circuit formed by a capacitor and a coil, resistive voltage dividers of the first and second transistor c, a blocking capacitor and a quartz resonator connected between the emitters of the transistors.

These schemes are widely known, have a number of positive properties and provide zero phase shift in the excitation circuit.

However, in generators built according to the Butler circuit, the input resistance of the emitter follower (EF) is mainly determined by the resistive voltage divider in the base circuit. In order for the input impedance of the electric drive to not shunt the oscillatory circuit of the cascade with OB, a rather high-resistance voltage divider is usually used in the base circuit of the cascade with OK. At the same time, to ensure stable operation of the cascade with OK when working in a wide temperature range and changing the supply voltage, the resistance of the voltage divider in the base circuit of the cascade with OK should be much less than the input resistance of the EP circuit.

The aim of the present invention is to increase the stability of the cascade with OK and the expansion of the temperature limits of the CG.

The essence of the invention lies in the fact that in a crystal oscillator containing two amplification stages on transistors, one of which is made with a common base, and the other with a common collector, an LC oscillatory circuit formed by a capacitor and an inductor and included in the collector circuit of the cascade transistor with OB, a quartz resonator connected between the emitters of transistors, according to the invention, a capacitor is inserted, which is connected between the emitter of the second transistor and the tap of the resistive voltage divider of the second trans a torus, and a choke, the first terminal of which is connected to a tap of the resistive voltage divider of the second transistor, and the second terminal is connected to the base of the second transistor. The indicated inclusion of the capacitor leads to a sharp increase in the input impedance of the electric drive at high frequencies, which reduces the resistance of the voltage divider in the base circuit of the cascade with OK, and the specified inclusion of the high-frequency inductor reduces the resistance to direct current in the base circuit of the cascade with OK in order to increase the stability of the operating mode scheme.

The drawing shows a schematic diagram of the proposed KG.

The crystal oscillator contains a first (1) transistor, the emitter of which is connected through a resistor (5) to a common power bus (17), a first (4 and 3) resistive voltage divider, which is connected between the power bus (16) and the common bus (17), the tap of which is connected to the base of the first (1) transistor, a blocking capacitor (12) connected between the common bus (17) and the base of the first (1) transistor, a second (2) transistor, the collector of which is connected to the power bus (16), and the emitter through a resistor (8) to a common bus (17), a second (7 and 6) resistive voltage divider, which includes between the power bus (16) and the common bus (17), the first (11) and second (18) isolation capacitors, an oscillating circuit consisting of a capacitor (10) and an inductor (9), a quartz resonator (13), which is connected between emitters of the first (1) and second (2) transistors. In this case, the first terminal of the inductor is connected to the first terminal of the capacitor, the second terminal is connected to the second terminal of the capacitor and the power rail, the first branch is connected to the collector of the first transistor, the second branch is connected through the first isolation capacitor with the base of the second transistor, and the third branch is connected to the first terminal of the second a separation capacitor, the second output of which is the output of the generator (the first, second and third taps divide the inductor into four parts, the number of turns in each of them is selected experimentally dependent aw of the parameters of the structural elements of the generator). Each voltage divider is a circuit of two series-connected resistors connected between the power bus and the common bus. Moreover, the connection of the tap of each voltage divider to the specified object provides the corresponding connection of the communication point between two series-connected resistors of the divider with the specified object.

A capacitor (15) is introduced into the crystal oscillator, which is connected between the emitter of the second transistor and the tap of the second resistive voltage divider, and a choke (14), the first pin of which is connected to the tap of the second resistive voltage divider, and the second pin is connected to the base of the second transistor.

The crystal oscillator operates as follows

When the power is turned on in the oscillatory circuit 9, 10, oscillations occur at the frequency of the series resonance of the quartz resonator 13 and go to the base of the transistor 2. Part of the signal from the emitter of the transistor 2 through the servo feedback circuit through the capacitor 15 and the inductor 14 goes to the base of the transistor 2, and the other part goes to the quartz resonator 13, included in the positive feedback circuit. Then the signal amplified by the transistor 1, enters the oscillatory circuit, closing the positive feedback circuit. The amplitude condition for the occurrence of oscillations in the generator is provided by the necessary voltage gain created by the exciter on transistors 1 and 2.

Due to the inclusion of a capacitor 15 and an inductor 14 in the servo feedback circuit, the input resistance of the cascade with OK increases, which reduces the resistance of the voltage divider (7 and 6) and improves the operation mode of transistor 2, so that the KG can operate in a wider temperature range. The output signal of the crystal oscillator is removed from the second output of the second isolation capacitor.

Thus, the use of servo feedback and the use of a throttle made it possible, preserving all the positive properties of the known circuit, to eliminate its shortcomings and thereby expand its operational capabilities.

Claims (1)

A crystal oscillator comprising a first transistor, the emitter of which is connected through a resistor to a common power bus, a first resistive voltage divider that is connected between the power bus and a common bus, the tap of which is connected to the base of the first transistor, an interlock capacitor connected between the common bus and the base of the first transistor , the second transistor, the collector of which is connected to the power bus, and the emitter through the resistor to the common bus, the second resistive voltage divider, which is connected between the power bus and the common bus, the second and second isolation capacitors, an oscillatory circuit consisting of a capacitor and an inductor, the first output of which is connected to the first output of the capacitor, the second output to the second output of the capacitor and the power rail, the first output to the collector of the first transistor, the second output to the first isolation capacitor - with the base of the second transistor, the third tap - with the first output of the second isolation capacitor, the second output of which is the output of the generator, a quartz resonator, which is connected between the emitter the first and second transistors, characterized in that a capacitor is inserted, which is connected between the emitter of the second transistor and the tap of the second resistive voltage divider and a choke, the first terminal of which is connected to the tap of the second resistive voltage divider, and the second pin to the base of the second transistor.