Oscillation circuit and electronic device

Abstract

The invention provides an oscillation circuit and an electronic apparatus. An oscillation circuit (1) is provided with: an oscillator (X1); a first capacitor (CF) having one end connected to the vibrator (X1); a second capacitor (CO) having one end connected to the other end of the first capacitor (CF); an output terminal (Vo) connected to a connection point (N2) of the first capacitor (CF) and the second capacitor (CO); an amplifier circuit (A1) connected between a connection point (N1) of the oscillator (X1) and the first capacitor (CF) and a connection point (N2) of the first capacitor (CF) and the second capacitor (CO), and forming an oscillation loop together with the first capacitor (CF); a differential amplifier circuit (A2) inserted into the oscillation loop; and a feedback path (3) configured so as to feed back a portion of the output generated at the output terminal (Vo) to the differential amplifier circuit (A2). As a result, high-speed start-up and high-frequency oscillation of the oscillation circuit are facilitated.

Description

Technical Field

[0001] The present invention relates to an oscillation circuit and electronic equipment using an oscillator. Background Art

[0002] In recent years, there has been a demand for longer battery life in IoT (Internet of Things) devices that connect mobile phones and personal belongings to the Internet. Therefore, reducing the power consumption of electronic circuits and electronic components used in these devices has become an important technical issue.

[0003] In the reference oscillation circuit used in small communication devices of IoT, the inverter-based Pierce circuit using an oscillator is widely used. Fig.11 As shown, the Pierce circuit 100 includes an IC200 and an oscillator X1. The IC200 includes a resistor R1, an inverter A3 connected in parallel with the oscillator X1, fixed capacitors C1a and C1b connected to one end and the other end of each of the resistor R1 and the inverter A3, and an active element A4. The oscillator X1 is arranged between the fixed capacitors C1a and C1b so as to be connected in parallel with the resistor R1. The circuit structure of the inverter-based Pierce circuit 100 is simple and easy to use. On the other hand, since the current flows in a steady state, there is a problem of high power consumption.

[0004] As a solution to the above-mentioned problem, a structure in which MOS transistors are used in complementation in a source follower Colpitts oscillation circuit is proposed in Patent Document 1. The source follower-based Colpitts oscillation circuit disclosed in Patent Document 1 successfully reduces the current consumption in the steady state (oscillation state) by one order of magnitude compared to the conventional Pierce circuit.

[0005] However, the Colpitts oscillation circuit based on the source follower has a problem of delayed oscillation start-up time compared with the conventional Pierce circuit.

[0006] Regarding the problem of oscillation start-up time delay, for example, in Patent Document 2, Fig.12 As shown, an oscillation circuit 400 including an inverter-based Pierce circuit 500 and a Colpitts oscillation circuit 600 is disclosed. The oscillation circuit 400 is configured such that the two oscillation circuits are switched by switches SW3 and SW4, and the inverter-based Pierce circuit 500 is used as a start-up circuit during oscillation startup, and the Colpitts oscillation circuit 600 is used as a steady-state circuit during steady-state oscillation.

[0007] However, in the transmission circuit 400 , when the Pierce circuit 500 and the Colpitts oscillation circuit 600 are switched, discontinuity may occur in the output voltage amplitude and the oscillation frequency.

[0008] Furthermore, in a Colpitts oscillation circuit using a source follower, if the oscillation frequency is high, a large negative resistance cannot be obtained, and therefore there is also a problem that the oscillation condition cannot be satisfied and the circuit does not oscillate.

[0009] Prior Art Literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent No. 6967248

[0012] Patent Document 2: Japanese Patent Application Publication No. 2022-131314 Summary of the invention

[0013] -Problems to be solved by the invention-

[0014] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an oscillation circuit that facilitates high-speed startup and high-frequency oscillation.

[0015] -Methods for solving problems-

[0016] An oscillation circuit according to one embodiment of the present invention comprises: an oscillator; a first capacitor having one end connected to the oscillator; a second capacitor having one end connected to the other end of the first capacitor; an output terminal connected to a connection point between the first capacitor and the second capacitor; an amplifier circuit connected between a connection point between the oscillator and the first capacitor and a connection point between the first capacitor and the second capacitor, and forming an oscillation loop together with the first capacitor; a differential amplifier circuit inserted in the oscillation loop; and a feedback path configured to feed back a part of the output generated at the output terminal to the differential amplifier circuit.

[0017] Furthermore, an electronic device according to an embodiment of the present invention includes the above-mentioned oscillation circuit.

[0018] -Effects of the Invention-

[0019] According to the present invention, it is possible to provide an oscillation circuit that facilitates high-speed startup and high-frequency oscillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a diagram showing a configuration example of an oscillation circuit according to the first embodiment of the present invention.

[0021] Figure 2A This is a diagram showing an example of an equivalent circuit of an oscillator.

[0022] Figure 2B A diagram showing a general equivalent circuit of an oscillation circuit.

[0023] Figure 3This is a diagram showing the frequency characteristics of the negative resistance of the Colpitts oscillator circuit when the differential amplifier circuit is disabled (OFF) in the oscillation circuit according to the first embodiment of the present invention and only the Colpitts oscillator circuit is used.

[0024] Figure 4 This is a diagram showing the frequency characteristics of the negative resistance when the differential amplifier circuit is enabled (ON) in the oscillation circuit according to the first embodiment of the present invention.

[0025] Figure 5 This is a diagram showing the frequency characteristics of the negative resistance when the differential amplifier circuit is enabled in the oscillation circuit according to the first embodiment of the present invention.

[0026] Fig. 6A It is a diagram showing a configuration example of a feedback amount adjustment circuit in the oscillation circuit according to the first embodiment of the present invention.

[0027] Figure 6B It is a diagram showing another configuration example of the feedback amount adjustment circuit in the oscillation circuit according to the first embodiment of the present invention.

[0028] Figure 7 It is a diagram showing a configuration example of an oscillation circuit according to a second embodiment of the present invention.

[0029] Figure 8 It is a diagram showing an example of oscillation amplitude start-up characteristics of the oscillation circuit according to the second embodiment of the present invention.

[0030] Fig. 9 It is a diagram showing a modification of the oscillation circuit according to the second embodiment of the present invention.

[0031] Fig.10 It is a diagram showing a configuration example of a switch in an oscillation circuit according to a second embodiment of the present invention.

[0032] Fig.11 This is a diagram showing a configuration example of an oscillation circuit using a conventional Pierce circuit.

[0033] Fig.12 This is a diagram showing a configuration example of an oscillation circuit that switches between a conventional Pierce circuit and a Colpitts oscillation circuit.

[0034] -Description of Reference Numerals-

[0035] 1…oscillation circuit, 2…feedback adjustment circuit, 3…feedback path, A1…amplification circuit, A2…differential amplifier circuit, X1…oscillator, CF, CO…oscillation capacitors. DETAILED DESCRIPTION

[0036] <First embodiment>

[0037] Figure 1 : is a diagram showing a configuration example of an oscillation circuit according to the first embodiment of the present invention. The oscillation circuit 1 according to the present embodiment has: an oscillator X1; a first capacitor CF having one end connected to the oscillator X1; a second capacitor CO having one end connected to the other end of the first capacitor CF; an output terminal Vo connected to a connection point N2 between the first capacitor CF and the second capacitor CO; an amplifier circuit A1 connected between the connection point N1 between the oscillator X1 and the first capacitor CF and the connection point N2 between the first capacitor CF and the second capacitor CO, forming an oscillation loop together with the first capacitor CF; a differential amplifier circuit A2 inserted in the oscillation loop; and a feedback path 3 configured to feed back a part of the output generated in the output terminal Vo to the differential amplifier circuit A2. In the oscillation circuit 1 according to the present embodiment, a feedback amount adjustment circuit 2 configured to adjust the feedback amount to the differential amplifier circuit A2 is also provided in the feedback path 3.

[0038] In the oscillation circuit 1 involved in this embodiment, the vibrator X1, the first capacitor CF, the second capacitor CO and the amplifier circuit A1 constitute a Colpitts oscillation circuit. Here, the amplifier circuit A1 can be a complementary source follower. For example, the amplifier circuit A1 can be constituted by a source follower in which an NMOS transistor and a PMOS transistor are cascade-connected.

[0039] The differential amplifier A2 includes a first input terminal VINP, a second input terminal VINN, and a differential output terminal VOUT. In the oscillation circuit 1 according to the present embodiment, the first input terminal VINP of the differential amplifier circuit A2 is connected to the connection point between the oscillator X1 and the first capacitor CF, and the differential output terminal VOUT of the differential amplifier circuit is connected to the input terminal of the amplifier circuit A1. In addition, the second input terminal VINN of the differential amplifier circuit A2 is connected to the feedback path 3. In the oscillation circuit 1 according to the present embodiment, as shown in FIG. Figure 1 As shown, the differential amplifier circuit A2 is inserted in the front stage of the amplifier circuit A1 in the oscillation loop including the amplifier A1 of the Colpitts oscillation circuit and the first capacitor CF, but as long as the phase condition maintained by the Colpitts oscillation circuit can be maintained, the position where the differential amplifier circuit A2 is inserted is not limited to the front stage of the amplifier circuit A1. For example, the differential amplifier circuit A2 may be inserted in the rear stage of the amplifier circuit A1, or may be inserted in the front stage or the rear stage of the oscillation capacitor CF in the oscillation loop.

[0040] Figure 2A The equivalent circuit of the resonator X1 is shown in FIG. The equivalent circuit of the resonator X1 can be represented by an equivalent series resistance Rm, an equivalent series capacitance Cm, and an equivalent series inductance Lm connected in series, and an equivalent parallel capacitance Cp connected in parallel with these. Figure 2BThe following shows a general equivalent circuit of an oscillation circuit using a piezoelectric vibrator. Figure 2B In the figure, the left side of the single-dot chain line represents the equivalent circuit of the oscillator, and the right side represents the equivalent circuit of the oscillation circuit. Rx is the equivalent series resistance of the oscillator side when loaded, and the load capacitance CL is the equivalent series capacitance of the oscillation circuit side viewed from the oscillator side. -Rn is the negative resistance of the oscillation circuit.

[0041] In order to oscillate, it is necessary to generate a negative resistance Rn on the oscillation circuit side to cancel the series equivalent resistance Rx on the vibrator side. By further increasing the value of the negative resistance Rn, the oscillation start-up time can be shortened.

[0042] In the oscillation circuit 1 involved in this embodiment, one side of the input terminal of the differential amplifier circuit A2 inserted in series in the oscillation loop of the Colpitts oscillation circuit, that is, the first input terminal VINP is directly connected to the connection point N1 of the oscillation loop, and a part of the output of the Colpitts oscillation circuit, that is, a part of the output of the amplifier circuit A1, is fed back via the feedback path 3 at the second input terminal VINN of the differential amplifier circuit A2.

[0043] In the path of the first input terminal NINP, the differential amplifier circuit A2 needs to maintain the phase condition maintained by the original oscillation loop including the first capacitor CF of the Colpitts oscillation circuit and the amplifier circuit A1, so the input-output phase difference of the differential amplifier circuit A2 is zero. In the path of the second input terminal VINN, by adjusting the feedback amount by the feedback amount adjustment circuit 2, a phase rotation corresponding to the feedback amount can be applied to the oscillation loop of the oscillation circuit 1. As a result, the frequency characteristics of the negative resistance can be changed.

[0044] Figure 3 to Figure 5 The graph shows the frequency characteristics of the negative resistance when the differential amplifier circuit A2 is enabled / disabled and the equivalent capacitance CL on the oscillation circuit side viewed from the vibrator X1 is changed under different feedback amounts when the differential amplifier circuit A2 is enabled. Figure 3 The frequency characteristic of the negative resistance when the differential amplifier circuit A2 is disabled is shown. Figure 4 as well as Figure 5 FIG. 4 shows the frequency characteristic of the negative resistance when the differential amplifier circuit A2 is enabled.

[0045] It is known that Figure 3 to Figure 5 In any of the above, the smaller the equivalent capacitance CL is, the easier it is to obtain a large negative resistance on the high-frequency side.

[0046] If we compare the negative resistance ( Figure 3 ) and the negative resistance when the differential amplifier circuit A2 is enabled ( Figure 4 , Figure 5 ), it can be seen that by enabling the differential amplifier circuit A2, at 50MHz, a negative resistance of about 10 times that of the case where only the Colpitts oscillation circuit is used can be obtained. In addition, at 100MHz, a negative resistance of 200Ω can be obtained, and even at this frequency, oscillation can be performed by the Colpitts oscillation circuit.

[0047] also, Figure 4 This shows the frequency characteristics when the differential amplifier circuit A2 is enabled and the feedback amount is small (K = 11 / 16). Figure 5 This shows the frequency characteristics when the differential amplifier circuit A2 is enabled and the feedback amount is large (K = 14 / 16). Figure 4 and Figure 5 By comparison, it can be said that the smaller the feedback amount, the more low-frequency oriented the frequency characteristic becomes.

[0048] Therefore, in order to facilitate high-frequency oscillation, it is sufficient to increase the feedback amount while reducing the load capacitance.

[0049] Fig. 6A as well as Figure 6B FIG. 1 is a diagram showing a configuration example of a feedback amount adjustment circuit in an oscillation circuit of the present invention. Fig. 6A In the embodiment, a feedback signal is input from a terminal VINN of the differential amplifier circuit. The differential pair transistors of the differential amplifier circuit (a transistor pair having VINN and VINP as input terminals) are each configured by, for example, 16 transistors connected in parallel. When the feedback amount is reduced, the number of operating transistors on the VINN side is reduced from 16. Specifically, the gate of the transistor is switched from the signal side to the GND side by a switch or the like to disconnect the transistor, thereby reducing the number of operating transistors and adjusting the feedback amount.

[0050] exist Fig. 6A In order to adjust the feedback amount, the number of operating transistors is controlled, but in Figure 6B In this case, the feedback amount is controlled by voltage division by resistors placed before the transistors instead of the number of transistors in operation. The feedback amount can also be controlled by replacing the resistors with capacitors in the same way of voltage division.

[0051] According to the oscillation circuit involved in this embodiment, high-speed startup and high-frequency oscillation can be facilitated. In addition, by connecting a differential amplifier circuit to the oscillation loop of the oscillation circuit, a part of the output of the amplifier circuit A1 is fed back to the second input terminal of the differential amplifier circuit A2, the negative resistance of the oscillation circuit can be increased, or the frequency characteristics of the negative resistance can be changed, so that high-speed startup and high-frequency oscillation can be easily achieved, and the degree of freedom in design is improved.

[0052] In addition, Fig.11In the conventional oscillation circuit, the frequency characteristics of the negative resistance can be changed by changing the oscillation capacitor. However, according to the oscillation circuit involved in this embodiment, an oscillation circuit with a high degree of design freedom can be realized compared with the conventional structure.

[0053] <Second embodiment>

[0054] Next, refer to Figure 7 to Figure 10 , an oscillation circuit according to a second embodiment of the present invention is described.

[0055] In the oscillation circuit according to the first embodiment of the present invention described above, the differential amplifier circuit A2 operates not only at the time of oscillation startup but also at the time of steady-state oscillation, so it is useful when the negative resistance is insufficient to maintain steady-state oscillation only by the amplifier circuit A1, but there is a problem that the oscillation noise characteristic is deteriorated by continuing to operate the differential amplifier circuit A2 also at the time of steady-state oscillation, thereby increasing the current consumption. In contrast, the oscillation circuit according to the second embodiment of the present invention is configured to switch between a first mode oscillation operation in which the differential amplifier circuit A2 is operated at the time of oscillation startup and a second mode oscillation operation in which the differential amplifier circuit A2 is stopped at the time of steady-state oscillation.

[0056] Figure 7 1 is a diagram showing a configuration example of an oscillation circuit according to a second embodiment of the present invention. In the oscillation circuit 1 according to the first embodiment of the present invention, the differential amplifier circuit A2 operates not only at the time of oscillation startup but also at the time of steady-state oscillation. In contrast, the oscillation circuit 1a according to the second embodiment of the present invention is configured to operate the differential amplifier circuit A2 only at the time of oscillation startup and to stop the operation of the differential amplifier circuit A2 at the time of steady-state oscillation.

[0057] Specifically, if Figure 7 As shown, the oscillation circuit 1a includes a switch SW1, which is arranged in parallel with the differential amplifier circuit A2, and selectively connects the first input terminal VINP and the differential output terminal VOUT of the differential amplifier A2 to each other, and is configured to switch between a first mode of oscillation operation for operating the differential amplifier circuit A2 when oscillation is started and a second mode of oscillation operation for stopping the operation of the differential amplifier circuit A2 during steady-state oscillation.

[0058] In this way, by switching between the oscillation action of the first mode and the oscillation action of the second mode, the operation of the differential amplifier circuit A2 is stopped during steady-state oscillation, thereby avoiding problems such as degradation of the oscillation noise characteristics and increase in current consumption caused by continuing the operation of the differential amplifier circuit A2 during steady-state oscillation.

[0059] However, in terms of switching the oscillation operation mode, the oscillation circuit 400 disclosed in Patent Document 2 (see Fig.12 ) In order to take into account both high-speed startup and low power consumption, the two oscillation circuits, the inverter-based Pierce circuit 500 and the Colpitts oscillation circuit 600, are switched by switches SW3 and SW4. During oscillation startup, only the inverter-based Pierce circuit 500 is used, and during steady-state oscillation, only the Colpitts oscillation circuit 600 is operated.

[0060] However, in Fig.12 In the configuration of the oscillation circuit 400 disclosed in Patent Document 2, when the two oscillation circuits 500 and 600 are switched, discontinuity in the output voltage amplitude and the oscillation frequency is likely to occur, which is a problem.

[0061] The discontinuity of the output voltage amplitude is caused by the fact that the Pierce oscillation circuit 500 based on the inverter oscillates easily saturates at a stage where the oscillation amplitude is small during startup. More specifically, the discontinuity of the oscillation frequency is caused by Fig.12 Among the three oscillation capacitors in the oscillation circuit shown, the only oscillation capacitor used in common during oscillation startup and steady-state oscillation is the oscillation capacitor C3. Although this oscillation frequency is not discontinuous and cannot be adjusted, it requires a lot of man-hours, so the product cannot be cheap.

[0062] On the other hand, in the oscillation circuit 1a according to the second embodiment of the present invention, Figure 7 As shown, the circuit that operates when the oscillation of the oscillation circuit starts is changed from the Pierce circuit based on the inverter to the differential amplifier circuit A2 with feedback control. Furthermore, it is provided with: a switch SW1 for bypassing the differential amplifier circuit A2 and connecting the input and output of the differential amplifier circuit A2 during steady-state oscillation; and an enable / disable input terminal for operating the differential amplifier circuit A2 during oscillation start and stopping the differential amplifier circuit A2 during steady-state oscillation.

[0063] In the oscillation circuit 1a involved in the second embodiment of the present invention, switching is performed between a first mode of oscillation operation in which the differential amplifier circuit A2 is operated at the start of oscillation and a second mode of oscillation operation in which the operation of the differential amplifier circuit A2 is stopped at the time of steady-state oscillation. In this way, by using the differential amplifier circuit A2 only at the start of oscillation, it is possible to solve the problem of the oscillation circuit 1 involved in the first embodiment of the present invention, that is, the problem of degradation of oscillation noise characteristics and increase in current consumption caused by continuing to operate the differential amplifier circuit A2 even at the time of steady-state oscillation.

[0064] Figure 8 Yes Fig.12 An example of the oscillation amplitude start-up characteristics of the oscillation circuit shown in FIG. 1 is compared with an example of the oscillation amplitude start-up characteristics of the oscillation circuit 1a involved in this embodiment. Figure 8 As shown in the upper layer, Fig.12The inverter-based Pierce oscillation circuit used at the start-up of the oscillation circuit shown is easily saturated at a stage where the oscillation amplitude is small, so the oscillation grows with amplitude steps from the start-up to the steady-state oscillation.

[0065] In the oscillation circuit 1a according to the present embodiment, the differential amplifier circuit A2 is used when the oscillation is started. Figure 8 As shown in the lower layer, it is possible to eliminate Fig.12 A problem in the oscillation circuit is the discontinuity of the output voltage amplitude.

[0066] Regarding the timing of the Colpitts oscillation circuit transitioning from oscillation startup to steady-state oscillation, i.e., the timing of switching the switch SW1 and disabling the differential amplifier A2, in order to make the transition of the oscillation frequency smooth, it is preferable to switch the switch at a stage where the oscillation amplitude at oscillation startup is stable to a certain extent. For example, the time point when the oscillation amplitude reaches 70% to 95% of the final convergence amplitude can be used as the switching timing of the switch.

[0067] In addition, by using the differential amplifier circuit A2 at the start of oscillation, the Fig.12 The oscillation circuit shown above has discontinuities in the output voltage amplitude and the oscillation frequency that are problematic.

[0068] In the oscillation circuit 1a involved in this embodiment, a source follower Colpitts oscillation circuit is used both at the oscillation startup and at the oscillation steady state, and the differential amplifier circuit A2 inserted in the oscillation loop is operated only at the oscillation startup. With such a structure, the oscillation capacitor used before and after the switching does not change, so the discontinuity of the oscillation frequency before and after the switching can be reduced.

[0069] Next, refer to Fig. 9 , Fig.10 , the switch SW1 in the oscillation circuit 1a according to the present embodiment will be further described.

[0070] The switch SW1 can be realized by a switch circuit composed of a switching transistor or a FET, for example. The trigger signal for switching the switch SW1 can be output from a circuit that monitors the oscillation amplitude of the oscillation circuit 1a, for example. Fig. 9 As shown in FIG. 1 , an oscillation amplitude detection circuit 4 is provided at the subsequent stage of the oscillation circuit 1a, and the oscillation amplitude detection circuit 4 is configured to output a control signal when the oscillation amplitude of the oscillation signal Vo of the Colpitts oscillation circuit becomes equal to or greater than a given reference value. Thus, the control signal output from the oscillation amplitude detection circuit 4 can be used as a trigger signal for switching the switch SW1 and enabling / disabling the differential amplifier A2.

[0071] The oscillation circuit 1a according to the present embodiment is configured to enable / disable the switch SW1 and the differential amplifier circuit A2 according to the control signal outputted by the oscillation amplitude detection circuit 4 based on the oscillation amplitude of the oscillation signal Vo of the oscillation circuit 1a, thereby switching from the first mode in which the differential amplifier circuit A2 is operated to the second mode in which the differential amplifier circuit A2 is disabled. Here, the switching condition of the time point when the oscillation amplitude of the oscillation circuit 1a reaches 70% to 95% of the final converged amplitude is an example, and in the oscillation amplitude detection circuit 4, the switching condition can be appropriately determined according to various conditions in the electronic device etc. to which it is applied.

[0072] The structure of the switch SW1 for switching from the first mode in which the differential amplifier circuit A2 is operated to the second mode in which the differential amplifier circuit A2 is deactivated is not limited to Figure 7 , Fig. 9 The illustrated structure.

[0073] Fig.10 1 is a diagram showing a specific configuration example of a switch in the oscillation circuit 1a according to the present embodiment. Fig.10 In the illustrated configuration example, the switch SW1 is a switch for switching a signal input to the amplifier circuit A1 as a complementary source follower. The switch SW1 is configured to connect the output terminal of the differential amplifier circuit A2 and the input terminal of the amplifier circuit A1 when the control signal is "high", and to connect the first input terminal VINP of the differential amplifier circuit A2 and the input terminal of the amplifier circuit A1 when the control signal is "low".

[0074] also, Fig.10 The switch SW2 shown is a switch for controlling the enable / disable of the differential amplifier A2. The output of the switch SW2 is connected to the current source control terminal of the differential amplifier circuit A2. When the control signal is "high", the switch SW2 selects the bias voltage VBN sufficient to operate the differential amplifier circuit A2, and when the control signal is "low", the switch SW2 selects the bias voltage VSS that disables the differential amplifier circuit A2.

[0075] The oscillation circuit used in this embodiment is basically a source follower Colpitts oscillation circuit at the time of oscillation startup and steady-state oscillation. The source follower Colpitts oscillation circuit has the characteristics of low current consumption setting and can be used with low noise.

[0076] In the oscillation circuit 1a involved in this embodiment, when the oscillation is started, the negative resistance is enhanced by operating the differential amplifier circuit A2, thereby shortening the oscillation start-up time and enabling high-frequency oscillation. On the other hand, during steady-state oscillation, the differential amplifier circuit A2 is stopped, and the value of the negative resistance is set to a relatively low value that can only maintain steady-state oscillation, thereby constituting a relatively low current consumption. Thus, the characteristics of the Colpitts oscillation circuit based on the source follower can be effectively utilized to easily perform high-speed startup and high-frequency oscillation.

[0077] When oscillating, the current consumption increases by the amount of differential amplifier circuit operation compared to steady-state oscillation, but the startup time is shortened to achieve the same effect. Fig.12 The oscillation circuit shown similarly reduces power consumption.

[0078] As described above, according to this embodiment, an oscillation circuit that facilitates high-speed startup and high-frequency oscillation can be realized. By applying the oscillation circuit of this embodiment to electronic devices such as mobile phones and IoT devices, it can contribute to low power consumption of electronic devices.

[0079] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0080] <Note>

[0081] Regarding the above-mentioned embodiment, the following additional notes are also disclosed.

[0082] <Note 1>

[0083] An oscillation circuit comprises: an oscillator; a first capacitor having one end connected to the oscillator; a second capacitor having one end connected to the other end of the first capacitor; an output terminal connected to a connection point between the first capacitor and the second capacitor; an amplifier circuit connected between a connection point between the oscillator and the first capacitor and a connection point between the first capacitor and the second capacitor, forming an oscillation loop together with the first capacitor; a differential amplifier circuit inserted in the oscillation loop; and a feedback path configured to feed back a part of an output generated at the output terminal to the differential amplifier circuit.

[0084] <Note 2>

[0085] The oscillation circuit according to Supplementary Note 1, further comprising: a feedback amount adjustment circuit provided in the feedback path and configured to adjust a feedback amount to the differential amplifier.

[0086] <Note 3>

[0087] An oscillation circuit according to Note 1 or 2, wherein the differential amplifier circuit comprises a first input terminal, a second input terminal and a differential output terminal, the first input terminal of the differential amplifier circuit is connected to a connection point between the oscillator and the first capacitor, the second input terminal of the differential amplifier circuit is connected to the feedback path, and the differential output terminal of the differential amplifier circuit is connected to the input terminal of the amplifier circuit.

[0088] <Note 4>

[0089] The oscillation circuit according to Supplementary Note 1 is configured such that: during oscillation startup, an oscillation operation of a first mode is performed to operate the differential amplifier circuit; during steady-state oscillation, an oscillation operation of a second mode is performed to stop the differential amplifier circuit.

[0090] <Note 5>

[0091] The oscillation circuit according to Supplementary Note 4, further comprising: a switch that selectively connects a first input terminal and a differential output terminal of the differential amplifier connected to the oscillation loop to each other.

[0092] <Note 6>

[0093] The oscillation circuit according to Note 4 further comprises: a detection circuit for detecting the oscillation amplitude of the oscillation circuit, wherein the detection circuit is configured to switch from the first mode to the second mode when the oscillation amplitude at the time of oscillation startup reaches 70% to 95% of the final convergence amplitude.

[0094] <Note 7>

[0095] The oscillation circuit according to any one of Supplementary Notes 1 to 6, wherein the amplifier circuit is a complementary source follower.

[0096] <Note 8>

[0097] An electronic device comprising the oscillation circuit according to any one of appendices 1 to 7.

[0098] Industrial Applicability

[0099] The present invention can be applied to an oscillation circuit used in a small electronic device.

Claims

1. An oscillator circuit, characterized in that: have: Vibrator; A first capacitor having one end connected to the vibrator; a second capacitor having one end connected to the other end of the first capacitor; an output terminal connected to a connection point between the first capacitor and the second capacitor; an amplifier circuit, connected between a connection point between the oscillator and the first capacitor and a connection point between the first capacitor and the second capacitor, and forming an oscillation loop together with the first capacitor; A differential amplifier circuit is inserted into the oscillation loop; as well as The feedback path is configured to feed back a part of the output generated at the output terminal to the differential amplifier circuit.

2. The oscillation circuit according to claim 1, wherein: The oscillation circuit further includes a feedback amount adjustment circuit provided in the feedback path and configured to adjust a feedback amount to the differential amplifier.

3. The oscillation circuit according to claim 1, wherein: The differential amplifier circuit includes a first input terminal, a second input terminal, and a differential output terminal. The first input terminal of the differential amplifier circuit is connected to a connection point between the vibrator and the first capacitor. The second input terminal of the differential amplifier circuit is connected to the feedback path. The differential output terminal of the differential amplifier circuit is connected to the input terminal of the amplifier circuit.

4. The oscillation circuit according to claim 1, wherein: The oscillation circuit is configured to perform an oscillation operation in a first mode to operate the differential amplifier circuit during oscillation startup, and to perform an oscillation operation in a second mode to stop the differential amplifier circuit during steady-state oscillation.

5. The oscillation circuit according to claim 4, wherein: The oscillation circuit further includes a switch that selectively connects a first input terminal and a differential output terminal of the differential amplifier connected to the oscillation loop to each other.

6. The oscillation circuit according to claim 4, wherein: The oscillation circuit further comprises: a detection circuit for detecting an oscillation amplitude of the oscillation circuit; The detection circuit is configured to switch from the first mode to the second mode when the oscillation amplitude at the time of oscillation startup reaches 70% to 95% of the final convergence amplitude.

7. The oscillation circuit according to claim 1, wherein: The amplifier circuit is a complementary source follower.

8. An electronic device, characterized in that: A device comprising the oscillation circuit according to claim 1.

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