JPH0441605Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Object of the Invention> [Industrial Application Field] The present invention relates to a direct compensation type temperature compensated crystal oscillation circuit.

[Prior Art] Temperature-compensated crystal oscillation circuits using a crystal resonator as an oscillation source have been widely used. For temperature compensation,
An indirect temperature compensation circuit that creates a DC temperature compensation voltage using a temperature sensing element such as a thermistor, and compensates it by adding a variable capacitance diode connected in series to a crystal resonator, and a temperature sensing element and a capacitor connected in series to the crystal resonator. There is a direct temperature compensation circuit that connects the two in parallel.

FIG. 3 shows a conventional direct compensation type crystal oscillation circuit. The temperature is compensated by the high temperature compensation circuit A and the low temperature compensation circuit B, which are circuits that combine a thermistor and a capacitor. Compensated. However, high-resistance thermistors are used as thermistors used in high-temperature compensation circuits, but high-resistance thermistors have poor temperature characteristics, making it difficult to perform temperature compensation. It also has poor high frequency characteristics. This is thought to be because when the thermistor has a high resistance characteristic, its capacitance increases, and this capacitance has poor temperature characteristics, resulting in poor temperature characteristics.

[Problems to be solved by the invention] Therefore, direct compensation is performed without using a high-resistance thermistor, but if a low-resistance thermistor is used, compensation can only be made on the low temperature side.

[Objective of the present invention] The present invention aims to provide an oscillation circuit that performs temperature compensation without using a high-resistance thermistor with poor temperature characteristics in a direct compensation type temperature compensation circuit.

<Structure of the present invention> [Means for solving the problem] Therefore, in a temperature-compensated crystal oscillator circuit comprising a temperature compensation circuit connected in series with a crystal resonator having temperature characteristics of a cubic function, the temperature compensation circuit is This problem is solved by connecting in series a temperature compensation capacitor with a negative first-order temperature coefficient that compensates for the low temperature side, and a temperature compensation circuit consisting of a temperature sensing element and a capacitor that compensates for the low temperature side.

[Operation and Examples] FIG. 1 is a circuit diagram showing an example of the present invention. The crystal resonator 1 has one terminal connected to an oscillation circuit 10.
and the other terminal is connected to temperature compensation circuit 2.
is connected. The configuration of the temperature compensation circuit includes a high temperature compensation capacitor 3 and a low temperature compensation circuit 4, and the low temperature compensation circuit 4 includes a thermistor 5 and capacitors 6 and 7. Capacitor 9 is a frequency adjustment capacitor.

In operation, the high temperature side compensation capacitor 3 is a temperature compensation capacitor having a negative first-order temperature coefficient, thereby changing the slope of the characteristic of the AT-cut crystal resonator having a cubic function. The characteristics of the crystal oscillator are determined in advance by using a frequency characteristic that rises below room temperature, and since the frequency slope is particularly large in the low temperature range, a thermistor and capacitor are used to compensate for this low temperature range. Create a compensation circuit to compensate. The thermistor used here is a low resistance thermistor. The thermistor has a temperature characteristic with a negative first-order coefficient, and as the temperature decreases, the resistance increases and the apparent capacitance of the capacitor 6 decreases, thereby increasing the frequency. This makes it possible to compensate for the temperature characteristics on the low temperature side.

In this way, a temperature compensation circuit that combines a thermistor and a capacitor is connected in series with a crystal resonator, and temperature compensation is performed by utilizing the fact that reactance changes with temperature.

In FIG. 2, the broken line shows the frequency-temperature characteristics of the crystal resonator, and the solid line shows the frequency-temperature characteristics of the temperature compensation circuit according to the present invention.

<Effects of the present invention> With the present invention, instead of using a high-resistance thermistor with poor high-frequency characteristics, a compensation circuit using a compensation capacitor and a capacitor for compensation on the high-temperature side and a low-resistance thermistor on the low-temperature side can be used. Stable compensation characteristics can be obtained, the number of parts is further reduced compared to the conventional system, and adjustment is easier.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a temperature-compensated crystal oscillation circuit of the present invention, FIG. 2 is a frequency-temperature characteristic diagram, and FIG. 3 is a conventional temperature-compensated crystal oscillation circuit. 1... Crystal resonator, 3... Temperature compensation capacitor, 5... Temperature sensing element, 6, 7... Capacitor.

Claims (1)

[Scope of utility model registration request] In a temperature compensated crystal oscillator circuit consisting of a temperature compensation circuit connected in series with a crystal resonator having temperature characteristics of a cubic function, the temperature compensation circuit has a temperature compensation circuit having a negative first-order temperature coefficient to compensate for the high temperature side. A temperature-compensated crystal oscillator circuit characterized in that a temperature-compensated circuit consisting of a capacitor, a temperature-sensitive element that compensates for the low-temperature side, and the capacitor is connected in series.