JPH02179105A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To facilitate circuit integration by constituting the circuit with a bridge circuit and a differential amplifier circuit. CONSTITUTION:A bridge circuit consists of resistors R1, R2, a crystal resonator Z, and a capacitor Ca, the resistors R1, R2 are connected in series, the crystal resonator Z and the capacitor Ca are connected in series to constitute a bridge. The connecting point between the resistors R1, R2 is connected to an output terminal of a differential amplifier circuit 1, the connecting point between the resistor R2 and the capacitor Ca is connected to an inverting input terminal of the differential amplifier circuit 1, and the connecting point between the resistor R1 and the crystal vibrator Z is connected to a noninverting input terminal of the differential amplifier circuit 1. Since the resonator Z is provided only between the differential amplifier circuit 1 and ground and small capacitance is enough for the added capacitor Ca, the added capacitor Ca is built in case of circuit integration and an exclusive terminal for mounting the vibrator Z externally is enough, then the circuit is advantages in the composite function processing of an IC.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an oscillation circuit, and more particularly to an oscillation circuit built into an IC (I product circuit).

Conventional oscillation circuits built into ICs include two-terminal type circuits and one-terminal type circuits, as shown in FIGS. 4 and 5. 2 pancreas 41 shown in Figure 4! The circuit connects the input and output of the inverter 3 provided in the IC to the external terminal T+ and T3, and connects the resistor R3 and crystal oscillator Z in parallel to the external terminal T2゜3. External terminal T2
, T3 and the ground were connected via capacitors 'j-Cz, Cs, in a so-called Colpitts type configuration.

Furthermore, in the one-terminal type circuit shown in FIG. 5, the input terminal of the amplifier circuit 4 is an external terminal T4, and a crystal camera Z is connected between the external terminal 4 and the ground. there were.

Problems to be Solved by the Invention However, the two-terminal type oscillation circuit shown in Fig. 4 has many parts that are externally attached, and two external terminals are also required, making it difficult to integrate the functions of the IC. The above is unfavorable.Also, the fifth
In the one-terminal oscillation circuit shown in the figure, in order to prevent spurious oscillations, it was necessary to provide capacitors C4 and C5 with relatively large capacitance on the output side of the amplifier circuit 4.
When trying to incorporate it into a device, there were problems such as difficulty in converting it into an IC.

The present invention has been made in view of the above points, and an object of the present invention is to provide an oscillation circuit that can be easily integrated into an IC.

Means for Solving the Problems The present invention provides a first resistor facing a capacitor and a second resistor facing a capacitor.
a bridge circuit configured such that a resistor is connected to the first resistor and faces the vibrator, and the output end is connected to the connection point of the first and second resistors, and The first input terminal f is connected to the connection point of the congen υ, and the first
The second input terminal is connected to the connection point between the resistor and the vibrator.

A working oscillator may be provided between the differential amplifier circuit and ground. In addition, since the resonator exhibits capacitance in the frequency range other than the resonance point and anti-resonance point of the resonator, the capacitance of the additional capacitor ω
By making M sufficiently smaller than the distance between the electrodes of the resonator, the impedance of the additional capacitor installed on the negative feedback loop side can be made larger than the impedance of the resonator installed on the positive feedback loop side. The gain of the negative feedback loop is larger than that of the feedback loop, and stable oscillation can be performed without causing abnormal oscillation. Therefore, stable oscillation is possible with a configuration in which the capacitance of the additional capacitor is small and the vibrator is provided between the differential amplifier circuit and the ground.

Embodiment FIG. 1 shows a block diagram of the principle of the present invention. 1 indicates a differential amplifier circuit, and Z indicates a crystal resonator.

The bridge circuit consists of resistors R+, R2, and a crystal-capturing r7° capacitor Ca, and the resistors R+ and R2 are connected in series, and the crystal resonator Z and capacitor Ca are connected in series to form the bridge. The connecting point between resistor R1 and resistor R2 of the bridge circuit is connected to the output terminal of differential amplifier circuit 1, the connecting point between resistor R2 and capacitor Ca is connected to the inverting input terminal of differential amplifier circuit 1, and resistor R+ A connection point with the crystal resonator 7 is connected to a non-inverting input terminal of the differential amplifier circuit 1. Further, the connection point between the crystal resonator 7 and the capacitor Ca is grounded.

Therefore, a positive feedback loop is formed by the resistor R+ and the mechanical vibrator Z, and a negative feedback loop is formed by the capacitor Ca added to the resistor R2, and oscillation is performed.

FIG. 2 shows a circuit diagram of an embodiment of the invention. The differential amplifier circuit 1 includes NPN transistors Tr1. King, 2° Tr32 paper anti-R resistance Rs, diode. Constant current source C, C+, C,
C2, the connection point between the diode D and the constant current sources C and C2 is the output terminal 2, the base of the transistor rr1 is the non-inverting input terminal, and the base of the transistor 'r2 is the inverting input terminal. The resistors R+ and R2 are configured to serve as both a phase shift resistor and a bias resistor.

Further, the common mode gain of the differential amplifier circuit 1 is set to approximately O, and the negative phase gain is set to approximately 10.

The equivalent circuit of the mechanical vibrator Z has a configuration as shown in FIG. 3, in which the electrode spacing flc+ is connected in parallel to a series circuit consisting of an inductance Lo, a capacitor fico, and a resistor ro. The reactance characteristic of the mechanical vibrator Z exhibits inductive properties in the region between the resonant frequency t's and the anti-resonant frequency fp, and exhibits capacitive properties in other regions. In addition, the electrode spacing I C+ is 5
The additional capacitor Ca provided on the negative feedback loop side is set to a small capacity of about several tens of P[, and C+>Ca. Therefore, in the frequency region between the resonance point and anti-resonance point of mechanical oscillator Z, the impedance between the non-inverting terminal and the ground is sufficiently smaller than the impedance between the inverting terminal and the ground, so the negative feedback loop is more important than the positive feedback loop. The gain on the side is loud. Therefore, abnormal oscillation (spurious oscillation) is less likely to occur.

Further, the additional capacitor Ca is the oscillation frequency f of the machine 5i11 child Z itself. The voltage e2 between the inverting input terminal and ground is slightly attenuated in the vicinity. Therefore, a differential input is effectively provided to the differential amplifier circuit 1. Therefore, a phase difference occurs, and the mechanical vibrator 7 oscillates at a frequency slightly shifted from its own parallel resonance frequency (anti-resonance frequency) fp. This deviation is extremely small and the oscillation stability is high.

Note that the differential amplifier circuit 1 is not limited to the configuration shown in FIG.
It is fine as long as it can be obtained to some extent.

Effects of the Invention As described above, according to the present invention, it is sufficient to provide the resonator between the input terminal of the differential amplifier circuit and the ground, and the capacitance of the additional capacitor may also be of small capacity. In this case, an additional capacitor υ can be built in, and only one dedicated terminal f is required when externally attaching a vibrator, which is advantageous when integrating the functions of an IC.

[Brief explanation of the drawing]

Fig. 1 is a principle block diagram of the present invention, Fig. 2 is a circuit diagram of an embodiment of the present invention, Fig. 3 is an equivalent circuit diagram of a crystal resonator, Fig. 4 is a conventional block diagram, and Fig. 5 is a circuit diagram of an embodiment of the present invention. A block diagram of another conventional example is shown. 1... Differential amplifier circuit, R+, R2... Resistor, Ca
...Capacitor, 2...Crystal resonator. Diagram

Claims (1)

[Claims] A bridge circuit configured such that a first resistor faces a capacitor, and a second resistor is connected to the first resistor and faces a vibrator; The output terminal is connected to the connection point between the second resistor and the capacitor, and the first output terminal is connected to the connection point between the second resistor and the capacitor.
An oscillation circuit comprising: a differential amplifier circuit to which an input terminal is connected, and a second input terminal is connected to a connection point between the first resistor and the vibrator.