RU2531871C1 - Quartz oscillator - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to the field of electronic technology and can be used for generation of electric signals stabilised with electromechanical resonators, namely in piezoelectric resonator transmitters. The quartz oscillator contains the quartz resonator and the unit of compensation of its direct capacitance including series connected first inverting amplifier and condenser, the second inverting amplifier, cascade non-inverting amplifier designed on two CMOS-transistors, phase corrector, the output of which is connected through the quartz resonator to the input of the cascade non-inverting amplifier, the output of which is connected to the input of the second inverting amplifier, the output of which is connected to the input of the phase corrector.

EFFECT: improvement of stability of the oscillator operation in various operating conditions.

3 dwg

Description

The invention relates to the field of electronic technology and can be used to generate electrical signals stabilized by electromechanical resonators, in particular in piezoresonance sensors.

The closest in technical essence to the claimed device is a crystal oscillator (see RF patent No. 2450415 dated 03/11/2011, published in B.I. No. 13 dated 05/10/2012), containing a crystal and a compensation unit for its static capacitance including a first inverting amplifier and a capacitor connected in series, wherein the second capacitor terminal and the input of the first inverting amplifier are connected to the terminals of the quartz resonator, respectively.

The above device is the closest in technical essence to the claimed and therefore selected as a prototype.

The disadvantage of the prototype is the relatively low value of the active load impedance of the quartz resonator and, accordingly, the low voltage value at the output of the quartz resonator, which requires the use of an amplifier with a high transmission coefficient.

The technical problem to be solved is the creation of a generator with a quartz resonator with an increased voltage at the load of the quartz resonator without losing its quality factor and reducing the requirements for the gain of the amplifier in the feedback loop.

Achievable technical result is to increase the stability of the generator in various operating conditions.

To achieve a technical result in a quartz oscillator containing a quartz resonator and a compensation unit for its static capacitance, including a first inverting amplifier and a capacitor connected in series, the second capacitor terminal and the input of the first inverting amplifier are connected to the quartz resonator terminals, respectively, new is that introduced a second inverting amplifier, the output of which is the output of the device, a cascode non-inverting amplifier, made on two CMOS transistors, and a phase corrector, the output of which through the quartz resonator is connected to the noninverting input cascode amplifier whose output is connected to the input of the second inverting amplifier, whose output is connected to the input of a phase corrector.

The figure 1 shows a functional diagram of the inventive generator. The figure 2 presents a diagram of one of the possible embodiments of the inventive generator. The figure 3 presents the equivalent circuit of a quartz resonator.

The quartz generator contains a quartz resonator 1 and a compensation unit for its static capacitance 2, including a first inverting amplifier 3 and a capacitor 4 connected in series, while the second output of the capacitor 4 and the input of the first inverting amplifier 3 are connected to the terminals of the quartz resonator 1, respectively, the second inverting amplifier 5 is introduced , the output of which is the output of the device, cascode non-inverting amplifier 6, made on two CMOS transistors, and phase corrector 7, the output of which is through quartz the resonator 1 is connected to the input of the cascode non-inverting amplifier 6, the output of which is connected to the input of the second inverting amplifier 5, the output of which is connected to the input of the phase corrector 7. In the non-inverting cascode amplifier 6, the transistor 11 is connected according to the circuit with a common source, and the transistor 12 with a common gate, the sources of transistors are combined. In this switching on of transistors, the passage capacitance from the output to the amplifier input (Miller capacitance) is eliminated, the input impedance is determined by the input capacitance of transistor 11 and the value of resistor 14. Transistor 11 and resistor 13 form a source follower, resistors 13, 14, 15 determine the operation mode of the transistor 11. The output stage of the cascode non-inverting amplifier 6 is made according to the scheme with a "common gate" on the transistor 12, the resistor 16 (cascade load). Resistors 13, 16, 17 give the transistor 12 a constant current mode. Capacitors 18, 19 eliminate the alternating voltage components at the drain of the transistor 11 and the gate of the transistor 12, respectively.

The device operates as follows. When voltage is supplied to the busbars from a constant voltage source (not shown in FIG. 1), the amplifiers 3, 5, 6 are set to active mode, providing the input AC voltage, for example, the noise voltage with increasing amplitude at its outputs in accordance with their transmission coefficients K ₅ , K ₆ . The output signal of the inverting amplifier 5 is transmitted through a phase corrector 7 with a transmission coefficient | K ₇ | <1. From the output of the phase corrector 7, an alternating voltage is applied to the input of the quartz resonator 1 and the input of the compensation unit of its static capacitance 2. When the value of the total transfer coefficient K _{Σ of the} feedback loop is greater than unity, conditions are created for self-generation at a frequency at which the condition of “phase balance” is fulfilled. In the transient mode, the amplitude of the alternating voltage rises from a practically “zero” value to values at which nonlinear distortions occur that impede the growth of the amplitude of the first harmonic. In this case, the total transmission coefficient becomes equal to unity K _∑ = 1.

The impedance of a quartz resonator 1 Z _{k is} equivalent to the impedance of a series L, C, R resonant circuit shunted by a parallel static capacitance C ₀ . At the frequency of the electric signal close to the frequency of the series resonance, the impedance Z _k is minimal and is determined mainly by the value of the active equivalent resistance R _k . In this case, the current at the output of the quartz resonator 1 will be maximum and is determined by the sum of the currents:

- series resonance current i _ZQ ;

- current of static capacitance C ₀ i _C0 .

The value of these currents is proportional to the voltage at the first output of the quartz resonator 1, which is equal to the output voltage of the phase corrector 7. The input voltage of the non-inverting amplifier 6 is determined by its input impedance and the sum of the output currents of the quartz resonator 1 and the static capacitance compensation unit 2:

$$U_{\mathrm{at}\mathrm{<figure-callout\; id="6"\; label="x"\; filenames="00000004.png"\; state="\{\{state\}\}">x</figure-callout>}6}=Z_{\mathrm{at}x6}\left(i_{ZQ}+i_{C0}+i_{\mathrm{to}\mathrm{about}m}\right),\left(\text{one}\right)$$

where i _ZQ is the series resonance current;

i _C0 — current of static capacitance of quartz resonator 1;

i _com is the output current of the static capacitance compensation unit 2;

Z _vh6 - input impedance of a non-inverting amplifier 6.

. Для обеспечения условия баланса фаз на выходе инвертирующего усилителя 5 включен фазовый корректор 7, фазовый сдвиг которого близок к - π/2(-90°). Таким образом, суммарный фазовый сдвиг между напряжением на первом выводе кварцевого резонатора 1 и напряжением на выходе фазового корректора 7 будет равен 2π(360°). Фазовый корректор 7 может быть выполнен, по крайней мере, на одной интегрирующей RC-цепи.The output current i _com of the static capacitance compensation unit 2 is determined by the transfer coefficient of the inverting amplifier 3 (set by the values of resistors 8, 9) and the value of the capacitance of the compensating capacitor 4. With these parameters, the value of the compensating current i _com is set close to the value of the current of the static capacitance i _C0 . The phase of the compensating current i _{com is} opposite to the phase of the current i _C0 due to the inverting amplifier 3 and the capacitive nature of the impedance of the compensating capacitor 4. Thus, in the input circuit of the amplifier 6, the current i _C0 will be compensated by the current i _com and the output voltage will be determined by the series resonance current of the quartz resonator 1 . The phase of the input and output voltages noninverting amplifier 6 is determined by the nature of its capacitive input impedance and the phase current i _ZQ, which is determined by the resistive-inductive character them edansa quartz resonator 1. The phase shift between the voltage at the first terminal of the quartz resonator 1 and the voltage at the noninverting input and the output of the amplifier 6 is close to π / 2 (-90 °). The inverting amplifier 5 creates a phase reversal of the signal by - π (-180 °). The total phase shift of the signal at its output relative to the phase at the input of quartz resonator 1 will be equal to - $$\frac{3}{2}\pi \left(-270°\right)$$

. To ensure the condition of the phase balance at the output of the inverting amplifier 5, a phase corrector 7 is included, the phase shift of which is close to - π / 2 (-90 °). Thus, the total phase shift between the voltage at the first output of the quartz resonator 1 and the voltage at the output of the phase corrector 7 will be 2π (360 °). Phase corrector 7 can be performed on at least one integrating RC circuit.

According to the invention, prototype generators were manufactured, tests of which confirmed their operability and effectiveness.

Claims (1)

A quartz oscillator comprising a quartz resonator and a compensation unit for its static capacitance, including a first inverting amplifier and a capacitor connected in series, the second capacitor terminal and the input of the first inverting amplifier connected to the terminals of the quartz resonator, respectively, characterized in that a second inverting amplifier, an output, is additionally introduced which is the output of the device, cascode non-inverting amplifier made on two CMOS transistors, phase corrector, output through which a quartz resonator is connected to the input of the cascode non-inverting amplifier, the output of which is connected to the input of the second inverting amplifier, the output of which is connected to the input of the phase corrector.

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