RU1782333C - Quartz generator - Google Patents

Description

(21) 4885262/09 (22) 11/26/90 (46) 12/15/92. Bull. No. 46 (76) V.G. Prokopenko

(56) Copyright certificate of the USSR M 1706002, cl. H 03 B 5/36, 07/07/89. (54) QUARTZ GENERATOR

(57) The invention relates to radio engineering and can be used as a highly stable reference frequency source. The aim of the invention is to increase frequency stability while expanding the range of load variations. The crystal oscillator contains the first, second, third, fourth, fifth and sixth transistors 1, 2, 3, 4, 5, 6, a quartz resonator (KP) 7, a resistor 8, the first and second current reflectors 9, 10, the first and second current sources 11. 12. In a crystal oscillator, the output signal is proportional to the Raman current, the volt-ampere characteristic of the active part is independent of the instability of the parameters of all transistors, and the first and second current reflectors provide increased frequency stability due to its independence from changes in loads. 2 ill.

Quartz about +

(L

WITH

vj

00

Yu

C)

with

Figure 1

The invention relates to radio engineering and is intended to be used as a highly stable reference frequency source as part of an economical small-sized electronic equipment.

A crystal oscillator is known that comprises an amplifier on a first transistor, negatively coupled through a first feedback transistor, having an active load consisting of a second transistor, negatively coupled through a second feedback transistor, and positively coupled through a quartz resonator.

The disadvantage of this generator is reduced frequency stability, as well as a high level of nonlinear distortion of the output signal.

A quartz oscillator is also known, comprising first and second transistors, which are positively coupled by a third and fourth feedback transistor, with the quartz resonator connected to a common bus with one output and the other ™ through a capacitor to the emitter of the first transistor.

The disadvantage of this crystal oscillator is the increased temperature and operational frequency instability due to the proportionality of the supply voltage of the active part of the generator and the bias currents of the transistors to the voltage of the biased p-n junction.

The closest in technical essence to the proposed one is a quartz oscillator containing a first transistor, the collector of which is connected to the first power bus, a second transistor, the emitter of which is connected to the emitter of the first transistor, a resistor, the first output of which is connected to the collector of the second transistor, the third transistor and quartz a resonator, the first terminal of which is connected to the first supply bus, the first and second transistors being made with the same type of conductivity, the third transistor is made with type n conductivity opposite to the type of conductivity of the first transistor.

The disadvantages of this crystal oscillator are reduced frequency stability and low load capacity. The frequency instability is due to the fact that in this generator only the low-signal value of the equivalent negative resistance of the active part of the generator is stabilized, in the region of signal limitation the current-voltage characteristic of the active part is determined by the uncompensated parameters of the transistors and is unstable, which leads to instability of the power dissipated by the piezoelectric element

quartz resonator Low load. the ability of this generator makes it possible for the generator to work only at a high resistance load, i.e. the range of variation of the generator loads is limited.

The purpose of the invention is to increase frequency stability while expanding the range of load variations.

The goal is achieved in that

5 to a crystal oscillator containing a first transistor, the collector of which is connected to the first power line, a second transistor, the emitter of which is connected to the emitter of the first transistor, a resistor,

0 the first terminal of which is connected to the collector of the second transistor, the third transistor and a quartz resonator, the first terminal of which is connected to the first power bus, while the first and second

5 transistors are made with the same type of conductivity, the third transistor is made with the type of conductivity opposite to the type of conductivity of the first transistor, additionally introduced

0 fourth, fifth and sixth transistors, first and second current sources and first and second current reflectors, the emitter of the third transistor connected to the base of the first transistor and the emitter of the fifth transistor, the base and collector of which are connected to the collector of the second transistor and to the base the sixth transistor, the collector of which is connected to the input of the first current reflector, the emitter of the sixth transistor is connected to the second output of the quartz resonator, the base of the second transistor and the emitter of the fourth transistor, the base of which dinena with the base and collector of the third transistor, the fourth transistor kollek5 torus connected to the input of the second current reflector, a first current source connected between a second supply rail and the collector of the third transistor, a second current source connected between the

0 by the second power bus and emitter of the first transistor, the second resistor pin is connected to the first bus, the power bus of the first and second current reflectors are connected to the first and second power buses, respectively, and the outputs of the first and second current reflectors are connected and are the output of the crystal oscillator, the fourth the transistor is made with a conductivity type identical to the conductivity type of the third transistor, and the fifth and

the sixth transistor is made with a conductivity type identical to the conductivity type of the first transistor.

A comparative analysis of the claimed technical solution, prototype, and analogs shows that the proposed crystal oscillator has the following new significant features: the active part of the generator is constructed in such a way that transistor pairs connected in parallel at a high frequency to the amplifying differential stage on the first and second transistors are used third-thursday and n-sixth transistors, which simultaneously serve to close the positive feedback loop in the active part and generator. In this case, the collector currents of the fourth and sixth transistors are summed at the output of the generator using current reflectors.

A positive effect is achieved due to the fact that, with the indicated transistors turned on, the formation of the current-voltage characteristics of the active part of the generator is carried out by comparing the base-emitter voltages of the transistors matched by parameters, which causes mutual compensation of the instability of their parameters over the entire working section of the current-voltage characteristics . By stabilizing the current-voltage characteristics of the active part of the generator, an increase in the stability of the power and spectral composition of the signal on quartz is achieved. The use of current reflectors at the generator output improves the spectral composition of the output signal, since a signal proportional to the quartz current is received at the output of the generator, the spectral composition of which is determined by the frequency-selective properties of the quartz resonator. In this case, the isolation of the generator and the load is improved, and the power of the output signal can be increased by increasing the transfer coefficient of current reflectors.

In FIG. 1 shows an electrical diagram of a crystal oscillator; in FIG. 2 - current distribution in the generator circuit during its operation.

The crystal oscillator contains the first 1, second 2, third 3, fourth 4, fifth 5 and sixth 6 transistors, a quartz resonator 7, a resistor 8, the first 9 and second 10 current reflectors, the first 11 and second 12 current sources.

We consider the operation of the proposed crystal oscillator under the following assumptions: transistors 1 and 2, 3 and 4, 5 and 6

identical, the base currents of transistors are negligible compared to their collector currents, transistors operate at frequencies much lower than fv, - the cutoff frequency of the current transistors in the circuit with a common base a.

Initially, voltages are supplied to the power buses and currents of current sources of such a magnitude as to bring all transistors into active mode. In this case, the emitter currents of the transistors 3, 4, 5, and 6 are set equal to the current loi of the current source 11, and the zitter currents of the transistors 1 and 2 are equal to half the current Io2 of the source

current 12, and oscillations are excited at the frequency of the series resonance of the quartz resonator. In this case, the quartz current of 1 kV supplied to the input of the active part of the generator (see Fig. 2) is divided by the current

And, flowing into the emitter of transistor 6 and flowing further to the input of current reflector 9, and current g flowing into the emitter of transistor 4 and then flowing to the input of current reflector 10, i.e.:

 + 12. (1)

In case of equality of the transfer coefficient of the current reflectors, the output current of the crystal oscillator is

(2)

where A is the transfer coefficient of current reflectors.

Currents ii and 12 cause a change in the base-emitter voltages of transistors 6 and 4, which leads to the appearance of alternating current 1z in the differential cascade by

transistors 1 and 2 supplied to the resistor 8.

We determine the value of current z. To do this, we sum the base-emitter voltages along the circuit formed by transistors 1,2, Zi4

11be2-ibe1 ibe4-ibeZ,

(3)

and along the circuit formed by the transistor - 50 mi 1,2, 6 and 5:

ibe2-ibe1 ibeb-ibe5.

(4)

where Ube is the base-emitter voltage of the 1st transistor.

Representing the values of the base-emitter voltages of the transistors using the Ebers-Mall equation, accurate to the value of the reverse current of the pn junction,

we transform equations (3) and (4) to the following form:

(5)

(6)

I02

101

where equation (5) is obtained from (3), and (6) from

(4).

Relations (5) and (6) allow us to express And and iz in terms of

1 I 01

2 I 01

1

I 02

1 +

I 02

- 1

1 t1 -21 s

I 02

(7)

1-yy

102

whence in accordance with (1) we get:

81 01/1 02

i sq - 1 s

1-(&

I 02

We transform (8) so that 1c is represented as a function of 1sq:

(9)

The high-frequency voltage on the quartz resonator is approximately equal to the voltage on the resistor 8, because the voltage drop across the low-resistance resistances of the emitter of transistors 4 and 6 can be neglected in comparison with it. Thus, the current-voltage characteristic of the active part of the generator is described by the following expression:

".V- tRSR ((o1

where R is the resistance of the resistor 8.

The dynamic resistance of the active part of the generator is equal to:

Ki J. (") b TG. b

At the same time, its low-signal value (at 1 kV - 0) is determined by the following relation:

1 g, I02

8 h oi

(")

It can be seen from expressions (10), (11), (12) that both the low-signal value of negative resistance and the current-voltage characteristic of the active part of the generator as a whole are determined only by the resistance of resistor 8 and currents of current sources 11 and 12 and not depends on transistor parameters. Since the stability of the parameters of the resistor and direct current sources is much higher than the stability of the parameters of transistors, there is an increase in the stability of the power dissipated

20 on a piezoelectric element of a quartz resonator, as well as stabilization of the spectral composition of the signal on quartz, which leads to an increase in the frequency stability of the proposed crystal oscillator.

25 From expression (2) it can be seen that the output signal in the crystal oscillator is proportional to the quartz current, i.e. its spectral composition is determined by the selectivity of the quartz resonator. At the same time, increase

30 VA, the current reflectors have a transfer coefficient A, it is easy to obtain an output current value that is approximately an order of magnitude higher than the quartz current value, and the maximum allowable voltage amplitude 35 at the external load also has an increased value and is approximately half the supply voltage. The introduction of current reflectors, in addition, provides additional isolation of the generator from the load circuits, which increases its reliability and widens the range of load variation.

Claims (1)

SUMMARY OF THE INVENTION 45 A crystal oscillator comprising a first transistor whose collector is connected to a first power rail, a second transistor whose emitter is connected to an emitter of a first transistor, a resistor, 50 a first terminal of which is connected to a collector of a second transistor, a third transistor and a quartz resonator, whose first terminal is connected to the first power bus, while the first and second transistors are made with the same type of conductivity, the third transistor is made with the type of conductivity opposite to the type of wire a first transistor, characterized in that, in order to increase frequency stability while expanding the load variation range, a fourth, fifth and sixth transistor, a first and second current source and a first and second current reflector are introduced, the emitter of the third transistor connected to the base of the first the transistor and the emitter of the fifth transistor, the base and collector of which is connected to the collector of the second transistor and the base of the sixth transistor, the collector of which is connected to the input of the first current reflector, the emitter of the sixth ican connected to the second terminal of the quartz resonator, the base of the second transistor and the emitter of the fourth transistor, whose base is connected to the base and collector of the third transistor, the collector of the fourth transistor w0 5 it is single with the input of the second current reflector, the first current source is connected between the second power line and the collector of the third transistor, the second current source is between the second power line and the emitter of the first transistor, the second output of the resistor is connected to the first power line, the power lines of the first and second current reflectors are connected respectively, to the first and second power buses, and the outputs of the first and second current reflectors are connected and are the output of a crystal oscillator, the fourth transistor is made with a conductivity type identical to the type of conductivity of the third transistor, and the fifth and sixth transistors with the type of conductivity identical to the type of conductivity of the first transistor. K & r $ $ th gene / mtor