SU1679599A1 - Crystal oscillator - Google Patents

Abstract

The invention relates to electronic engineering and can be used in electronic clocks. The purpose of the invention is to increase the stability of the amplitude of the output oscillations. The quartz generator contains an inverting amplifier 1, a n-channel MOS transistor 2, a p-channel MOS transistor 3, the first 4 and second 5 capacitors, a quartz resonator 6, and a threshold voltage generator 7. The frequency driver circuit of the quartz oscillator is made on capacitors 4 and 5 and quartz resonator 6. Transistors 2 and 3 are included in the negative feedback circuit of inverting amplifier 1. The threshold voltage at the gates of transistors 2 and 3 is set by shaper 7 so as to provide stabilizing the amplitude of the output oscillations due to the change in the resistance of the channels of transistors 2 and 3 with a minimum shunting of the quartz resonator 6. 3 Il. cl

Description

The invention relates to electronic engineering and can be used in electronic clocks.

The purpose of the invention is to increase the stability of the amplitude of the output oscillations.

Figure 1 shows a structural electrical circuit of a quartz oscillator; Fig. 2 shows an embodiment of a form voltage driver; Figs. 3 are graphs illustrating the principle of operation of a quartz oscillator.

The quartz generator contains an inverting amplifier 1, n-channel MOS transistor 2, p-channel MOS transistor 3. the first 4 and second 5 capacitors, a quartz resonator 6, the driver 7 threshold voltages.

The shaper 7 contains a p-channel MOS transistor 8. p-channel MOP transistor 9, the first 10 and second 11 current transistors.

Inverting amplifier 1 contains l-channel MOSFET 12 and p-channel MOSFET 13.

Quartz generator works as follows.

Characteristic modes of operation of a quartz oscillator are (see Fig. 3), the startup mode I and the stationary oscillation mode P.

When the power supply is connected and any change in the supply voltage, the drain voltages of the p-channel MLP transistor 9 and n-channel MOS transistor 8 of the driver 7 do not change.

At the first moment after connecting the power source, the first capacitor 4 is discharged, at the input of the quartz oscillator

with

4 О СЛ Ч) О

common bus potential, p-channel MOS transistor 13 of inverting amplifier 1 is locked, n-channel MOS transistor 12 of inverting amplifier 1 is open, and the output of inverting amplifier 1 is voltage -E.

In this case, the p-channel MOS transistor 3 is locked at the source, and the n-channel MOS transistor 2 is open by the voltage on its gate. The drain current of an n-channel MOS transistor 2 charges the first capacitor 4 until the input voltage of inverting amplifier 1 is equal to the threshold voltage of p-channel MOS transistor 13 of inverting amplifier 1. At this moment, inverting amplifier 1 is is in linear mode and the n-channel MOS transistor 2 is instantly locked. The inverting amplifier 1 in the linear mode has a large voltage gain (on the order of 100-20.0). The shunt effect from the feedback elements for inverting amplifier 1 and quartz resonator 6 is absent, since the n-channel MOS transistor 2 and the p-channel MOS transistor 3 are locked by voltage on their sources.

The voltage at the output of the inverting amplifier 1, which differs from the voltage 0 or -E by only 30-50 mV, blocks the n-channel MOS transistor 2 and the p-channel MOS transistor 3.

In a quartz oscillator, an oscillatory process begins to develop with an increasing amplitude of oscillations. Finally, the quartz oscillator goes into a stationary mode of oscillation, where the double amplitude of oscillation at the output is equal to E.

Fig. 3 shows diagrams of the input and output voltages of a quartz oscillator in the processes of starting and going into the stationary oscillation mode.

In mode II, stationary oscillations at the input of an inverting amplifier 1. The signal is usually sinusoidal, and at the output - rectangular or trapezoidal. transistor 12 of the inverting MOS amplifier 1 is open p-channel MOS transistor 3, and in the opposite state of inverting amplifier 1 is open n-channel MOS transistor 2.

One of the conditions for the stability of the steady state oscillation of the crystal oscillator is the stabilization of the operating point of the inverting amplifier 1 at the input around which oscillations occur.

In turn, the condition of stability of the operating point at the input of amplifier 1 is the equality O of the voltage change on the first capacitor A in two cycles (one

period) oscillations of the crystal oscillator 1. With equal currents, respectively, of the p-channel MOS transistor 2 and p-channel MOS transistor 3 g, the balance condition corresponds to the equality (duration) of cycles ti and ta. If, for any reason, it happens to be 12, then the operating point of the inverting amplifier 1 at the input shifts in the direction of the potential of the common bus, which reduces the duration

5 of the first cycle ti and increases the duration of the second cycle t2 until the duration of these cycles ti 12 is equalized. Sometimes this automatic balancing of the crystal oscillator occurs

0 for several periods.

The operation of the quartz oscillator in the mode of high pulse currents 2 and 3 allows to reduce the time ti and ta, during which the inverting MOS amplifier 1

5 is in a non-linear region, so that the shape of the output voltage is close to the sinusoidal one and the parasitic power is reduced by distorting the shape of the output voltage.

0 In the driver of the 7 threshold voltages, instead of the first 10 and second 11 current generators, either resistors or combinations of transistors and resistors can be used, connected in accordance with the scheme in Fig. 2. A compensated trigger circuit (see FIG. 2), where the positive feedback (OS) of the two amplification stages is compensated for by the negative gate-drain OS, the source-substrate

0 inside the cascades, physically realizes in the best way conditional load current generators 10, 11 of the driver 7 reference voltages.

Claims (1)

Invention Formula 5 A crystal oscillator containing an inverting amplifier, which is connected between the supply bus and a common bus, a first capacitor, which is connected between the input of the inverting amplifier and a common bus, a second capacitor, which is connected between the output of the inverting amplifier, and a common crystal, which is connected between input and output of the inverting amplifier, n-ka5 nalny MOS transistor, the drain and source of which are connected respectively to the output and input of the inverting amplifier, p-channel MOS transistor, drain and source to which are connected respectively to the output and input of the inverting amplifier, characterized in that, in order to increase the stability of the output oscillation amplitude, a threshold voltage shaper is introduced into it, which is made on a p-channel MOS transistor, the source and substrate of which are connected to the common bus, and the drain and gate through the first current generator to power bus, n-channel MOS transistor, the source and substrate of which are connected to the power bus, and the drain and the gate through the second current generator to 0 common bus, while the gate of the p-channel MOS transistor is connected to the drain of the p-channel MOS transistor of the threshold voltage driver, the gate of the n-channel MOS transistor is connected to the drain of the n-channel MOP transistor of the threshold voltage generator, the substrate n- a channel MOS transistor and a p-channel MOS transistor are connected respectively to the power bus and the common bus. figure 1 1 In I | .J eight R I n YU IT..J FIG. I By t