JP2007318204A - Oscillation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise a negative resistance of an oscillation device without reducing a base current. <P>SOLUTION: The oscillation device includes: an oscillation circuit having a bipolar transistor and a piezoelectric vibrator connected to a base of the bipolar transistor; an inverter element having an input end connected to a base electrode of the bipolar transistor; and a resistor connected between an input end of the inverter element and an output end thereof. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an oscillation device that generates an oscillation signal having an oscillation frequency defined by a piezoelectric vibrator such as a crystal vibrator, which can be used for chemical or medical sensing (detection).

As shown in FIG. 7, the conventional oscillating device OD10 includes transistors TR1 and TR2 that are cascode-connected to each other to form, for example, a Colpitts type oscillation circuit. More specifically, the transistor TR1 has a grounded emitter. And the base and ground potential GN
A crystal resonator X1 is connected between D, and the transistor TR2 is grounded at the base. The resistor RB1 is used to define the base potential of the transistors TR1 and TR2.
, RB2 and RB3 are connected in series between the power supply potential Vcc and the ground potential GND.

The oscillation device OD10 illustrated in FIG. 7 can be represented by the equivalent circuit illustrated in FIG. Here, the impedance of the crystal resonator X1 is zxt, and the resistance R of the circuit elements other than the crystal resonator X1
The relationship between bci and capacitive reactance Cbci is given by equation (1).

（１）式中の抵抗Ｒｂｃｉは、（２）式で表される。

The resistance Rbci in the equation (1) is expressed by the equation (2).

トランジスタＴＲ１、ＴＲ２のベース・エミッタ間の等価抵抗をＲπ、等価容量をＣπ
、トランジスタＴＲ１、ＴＲ２の電流増幅率をｈｆｅとし、また、ベース・エミッタ間電
圧をＶｂｅ≒０．７Ｖであるとすると、（３）式が与えられる。

The equivalent resistance between the base and emitter of the transistors TR1 and TR2 is Rπ, and the equivalent capacitance is Cπ.
Assuming that the current amplification factors of the transistors TR1 and TR2 are hfe and the base-emitter voltage is Vbe≈0.7V, the equation (3) is given.

ここで、τＦは、順方向ベース走行時間、ｇｍは、相互インダクタンス、Ｉｃは、コレ
クタ直流電流、Ｒ３は、エミッタ抵抗、Ｒｂは、ベースバイアス抵抗である。

Here, τF is the forward base travel time, gm is the mutual inductance, Ic is the collector DC current, R3 is the emitter resistance, and Rb is the base bias resistance.

Based on the equation (3), the resistance Rbci shown in the equation (2) is Vcc = 3.3 V, C =
C2 = C3 (variable), R3 = 1 kΩ, Rb = 5 kΩ, hfe = 200, τF = 01nse
c, gm = 38 mA / V × Ic, Rπ = hfe / gmCπ = τF × gm, Vbe = 0.7
When simulation is performed under the condition of Vdc, the graph shown in FIG. 9 can be obtained. The graph shows that the absolute value of the negative resistance is approximately 2.5 kΩ regardless of whether the capacitor C (C2, C3) is 15 pF or 55 pF.

For example, when the oscillation device OD10 is used in an environment where it is difficult to oscillate mechanically such as the above-described sensing, the absolute value of the negative resistance is desirably larger in order to make the oscillation electrically easy. . Theoretically, the absolute value of the negative resistance increases as the resistance values of the resistors RB2 and RB3, which appear to be connected in parallel with each other from the crystal resonator X10, are increased.

However, if the resistance values of the resistors RB2 and RB3 are increased, the transistor TR
Since the base current of 1 cannot sufficiently flow, there is a limit to increasing the resistance values of the resistors RB2 and RB3. In the conventional oscillation device OD10 described above, the value of the negative resistance is There was a problem that it was difficult to make it larger than the above value.

In order to solve the above problems, an oscillation device according to the present invention has an oscillation circuit having a bipolar transistor and a piezoelectric vibrator connected to the base of the bipolar transistor, and an input terminal connected to the base electrode of the bipolar transistor. And a resistor connected between an input terminal and an output terminal of the inverter element.

According to the above-described oscillation device according to the present invention, the potential of the base of the bipolar transistor to which the piezoelectric vibrator is connected is connected to the potential of the input terminal of the inverter element by the cooperation of the inverter element and the resistor. Since it is specified by specifying, the base current of the bipolar transistor is reduced as compared with the case of specifying by the resistance voltage division by two resistors provided between the power supply potential and the ground potential as in the conventional case. Therefore, the negative resistance of the oscillation device can be increased.

In the above-described oscillation device according to the present invention, the bipolar transistor is applied with a first power supply potential for driving the bipolar transistor, and the inverter element is a second power source for driving the inverter element. The second power supply potential which is a power supply potential and is different from the first power supply potential is applied.

In the oscillation device according to the present invention described above, the inverter element is connected via the first resistor.
One of the power supply potential and the ground potential for driving the inverter element is applied, and the other potential is applied via the second resistor.

  Embodiments of an oscillation device according to the present invention will be described with reference to the drawings.

"Example"
As shown in FIG. 1, the oscillation device OD of the embodiment includes a transistor TR1, a crystal resonator X1, an inverter element IN1, resistors R1, R2, and R3, capacitors C1, C2,
Cx, Cp1, Cp2, and Cp3.

The transistor TR1 is an NPN bipolar transistor, and a resistor R3 and a capacitor C2 are connected in parallel between the emitter and the ground potential GND in order to form a Colpitts oscillation circuit in cooperation with the crystal resonator X1. The capacitor C1 is connected between the base and the emitter, and the input terminal of the inverter element IN1 is connected to the base.
A crystal resonator X1 and a capacitor (variable capacitor) Cx are connected in series between the base and the ground potential GND, and a resistor R2 is connected between the collector and the power supply potential Vcc.

The inverter element IN1 is composed of, for example, a CMOS inverter element, and a resistor R1 is connected between an input end and an output end, and the input end of the resistor R1 is applied to the power supply potential applied to the inverter element IN1. It is stably maintained at an intermediate potential (for example, +2.5 V) between Vcc (for example, +5 V) and the ground potential GND.

Bypass capacitors Cp1 and Cp2 are provided between the power supply potential Vcc and the ground potential GND, and a coupling capacitor Cp3 is connected to the output terminal OUT1.

The oscillation device OD illustrated in FIG. 1 can be represented by an equivalent circuit OD (e) illustrated in FIG.
In the equivalent circuit OD (e), from the relationship between current and voltage under Kirchhoff's law, (4)
Equations (5) and (6) are obtained.

（４）式〜（６）式より、発振の臨界条件を示すインピーダンス条件は、（７）式で与
えられ、また、アドミタンス条件は、（８）式で与えられる。

From the equations (4) to (6), the impedance condition indicating the critical condition for oscillation is given by the equation (7), and the admittance condition is given by the equation (8).

（８）式における、ｚ１、ｙ２、ｙ３を、（９）式のように置き換えると、発振装置Ｏ
Ｄにおける水晶振動子Ｘ１以外の回路素子の抵抗Ｒｉｃｉ、容量性リアクタンスＣｉｃｉ
は、（１０）式により与えられる。

When z1, y2, and y3 in equation (8) are replaced as in equation (9), the oscillation device O
The resistance Rci of the circuit elements other than the crystal resonator X1 in D and the capacitive reactance Cci
Is given by equation (10).

（１０）式に示される抵抗Ｒｉｃｉ、容量性リアクタンスＣｉｃｉは、（１１）式で与
えられる。

The resistance Rici and the capacitive reactance Cici shown in the equation (10) are given by the equation (11).

ここで、（１１）式に示されるコンダクタンス及びサセプタンスは、（１２）式で表さ
れる。

Here, the conductance and susceptance shown in the equation (11) are expressed by the equation (12).

図３は、図１に図示された実施例の発振装置のシミュレーションの結果を示す。図３に
図示のグラフでは、Ｒ３＝１ｋΩ、２ｋΩ、３ｋΩのとき、負性抵抗は、それぞれ、約１
２ｋΩ、約２５ｋΩ、３８ｋΩであり、従来の発振装置ＯＤ１０における負性抵抗の２．
５ｋΩより大きくなっている。ここで、当該シミュレーションは、Ｖｃｃ＝３．３Ｖ、Ｃ
２＝Ｃ３＝１５ｐＦ、インバータ素子ＩＮ１について、ｇｍ＝１μＡ／Ｖであり、また、
トランジスタＴＲ１について、Ｖｂｅ＝０．７Ｖ、ｈｆｅ＝２００、τＦ＝０．１ｎｓｅ
ｃ、ｇｍ２＝３８ｍＡ／Ｖ×Ｉｃ、Ｒπ＝ｈｆｅ／ｇｍ２、Ｃπ＝τＦ×ｇｍ２という条
件の下に行われている。

FIG. 3 shows a result of simulation of the oscillation device of the embodiment shown in FIG. In the graph shown in FIG. 3, when R3 = 1 kΩ, 2 kΩ, 3 kΩ, the negative resistance is about 1 respectively.
2 kΩ, about 25 kΩ, and 38 kΩ, which are the negative resistances of the conventional oscillation device OD10.
It is larger than 5 kΩ. Here, in the simulation, Vcc = 3.3V, C
2 = C3 = 15 pF, for inverter element IN1, gm = 1 μA / V, and
For transistor TR1, Vbe = 0.7V, hfe = 200, τF = 0.1nse
c, gm2 = 38 mA / V × Ic, Rπ = hfe / gm2, and Cπ = τF × gm2.

As described above, in the oscillation device OD of the embodiment, the inverter element IN1 and the resistor R1 cooperatively define the base of the transistor TR1 to which the crystal resonator X1 is connected. Since the potential is applied, the potential is applied to the base by the resistance voltage division by a plurality of resistors connected in series between the power supply voltage Vcc and the ground potential GND as in the conventional oscillation device OD10. In contrast, the negative resistance can be increased without reducing the base current of the transistor TR1.

<< Modification 1 >>
Instead of driving the transistor TR1 and the inverter element IN1 with the same power supply potential Vcc (for example, + 5V) like the oscillation device OD of the embodiment, as shown in FIG.
The transistor TR1 is driven with a power supply potential Vcc1 (for example, + 5V), and on the other hand, the inverter element IN1 is driven with another power supply potential Vcc2 (for example, + 3V), thereby providing the base of the transistor TR1 with the power supply potential Vcc2 and the ground potential. Intermediate potential between GND, for example
By applying +1.5 V, the value of the negative resistance of the oscillation device OD1 of the first modification can be made different from that of the oscillation device OD of the embodiment.

<< Modification 2 >>
Instead of applying the power supply potential Vcc and the ground potential GND directly to the inverter element IN1, such as the oscillation device OD of the embodiment, as shown in FIG. 5, the inverter element IN1
The power supply potential Vcc (for example, + 5V) is applied to the first through the resistor R4, and the resistor R
The ground potential GND is applied via 5. Thereby, the resistor R is connected to the inverter element IN1.
4 is defined as, for example, + 2V, and the potential at the point P2, where the resistor R5 is connected to the inverter element IN1, is, for example, 0.
It is specified to 5V. As a result, the base of the transistor TR1 is connected to the potential at the point P1 and the point P1.
2 is set to + 1.25V, which is an intermediate potential between the potential of 2 and the oscillation device O of Modification 2
It becomes possible to make the value of the negative resistance of D2 different from the value of the negative resistance of the oscillation device OD of the embodiment.

<< Modification 3 >>
In the oscillation device OD of the embodiment, instead of the Colpitts type oscillation circuit, a Peers CB type oscillation circuit as shown in FIG. 6 is used, and the base of the Peers type oscillation circuit is defined by the inverter element IN1 and the resistor R1. By applying the potential at the input terminal of the inverter element IN1, the negative resistance of the oscillation device OD3 of the third modification can be increased without reducing the base current, as described above.

The figure which shows the structure of the oscillation apparatus of an Example. The figure which shows the equivalent circuit of the oscillation apparatus of an Example. The graph which shows the simulation result of the oscillation apparatus of an Example. The figure which shows the structure of the oscillation apparatus of the modification 1. FIG. The figure which shows the structure of the oscillation apparatus of the modification 2. The figure which shows the structure of the oscillation apparatus of the modification 3. The figure which shows the structure of the conventional oscillation apparatus. The figure which shows the equivalent circuit of the conventional oscillation apparatus. The figure which shows the result of the simulation of the conventional oscillation apparatus.

Explanation of symbols

OD ... oscillator, TR1 ... transistor, IN1 ... inverter element, X1 ... crystal oscillator, R5 ... resistor.

Claims (3)

An oscillation circuit having a bipolar transistor and a piezoelectric vibrator connected to a base of the bipolar transistor;
An inverter element having an input terminal connected to the base electrode of the bipolar transistor;
And a resistor connected between an input terminal and an output terminal of the inverter element. The bipolar transistor is applied with a first power supply potential for driving the bipolar transistor,
The second power supply potential that is a second power supply potential for driving the inverter element and that is different from the first power supply potential is applied to the inverter element. 1. The oscillation device according to 1. The inverter element is applied with one of a power supply potential and a ground potential for driving the inverter element through the first resistor, and the other resistor through the second resistor. The oscillation device according to claim 1, wherein a potential is applied.

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