JPH04298103A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To optimize an oscillating condition over a wide frequency range by making a feedback resistance value adjustable in an inverter oscillation circuit. CONSTITUTION:A feedback resistance between the drain and the gate of an inverter 1 is varied for 2 steps or over by combining 'connection' and 'nonconnection' of option pads 10, 12 to the terminal of a piezoelectric vibrator 7 connecting to a drain pad 6. When the oscillating frequency is low, the feedback resistance is increased without connecting the option pads and when the oscillating frequency is conversely high, the option pads are connected to decrease the feedback resistance, thereby optimizing the oscillating condition.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillation circuit constructed using an inverter system.

0002

2. Description of the Related Art An example of a conventional oscillation circuit is shown in FIG.

In the figure, 101 is an inverter, for example, a high-speed CMOS that can operate at a desired oscillation frequency.
This is an inverter. And this inverter 101
A gate capacitor 102, a drain capacitor 103, and a feedback resistor 104 are connected to the gate capacitor 102 and the drain capacitor 103. A piezoelectric vibrator 107 is connected to this via a gate pad 105 and a drain pad 106 by wire bonding or the like. 108 is an output buffer that amplifies the oscillation waveform.

In the oscillation circuit configured in this manner, the oscillation frequency band in which the piezoelectric vibrator stably oscillates is determined by the amplification factor of the inverter 101 and the gate capacitance 102.
, a drain capacitance 103 , and a feedback resistor 104 . Among these, the feedback resistor 104 can particularly change the frequency band significantly, and specifically, it is shown in FIG.
The resistance value is set based on the characteristic diagram shown in . FIG. 4 is a negative resistance characteristic diagram viewed from the piezoelectric vibrator to the circuit side, showing that the frequency where negative resistance exists can be oscillated, and
The larger the negative resistance value, the more oscillation margin there is (easier to oscillate). Looking at it this way, the resistance is high in the low frequency band, and the higher the frequency, the smaller the resistance value. For example, determine the feedback resistance as shown in Table 1.

[Table 1] If the above settings are not changed, the piezoelectric vibrator will not oscillate at the desired order, but will oscillate at another order, that is, at another frequency. For example, if an attempt is made to oscillate a vibrator with a fundamental wave of 10 MHz using a feedback resistor of 6 KΩ, it will oscillate with a tertiary wave of 30 MHz. If you try to oscillate a 60MHz vibrator with a tertiary wave using a feedback resistance of 4KΩ, it will oscillate at the fundamental wave of 20MHz. therefore,
The feedback resistance must be set at an optimal value for the oscillation frequency.

[0005]

[Problem to be Solved by the Invention] However, in the conventional oscillation circuit having the configuration shown in FIG. 5, the feedback resistance is fixed, so when trying to set the feedback resistance according to the oscillation frequency band, , it is necessary to prepare as many oscillation circuits as there are oscillation frequency bands. IC oscillation circuit
If the number of ICs is the same, you must prepare the same number of ICs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an oscillation circuit that can oscillate in a wide frequency band under optimal oscillation conditions using one type of oscillation circuit, particularly one type of oscillation circuit IC.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the oscillation circuit of the present invention includes an inverter, a gate capacitor connected to the gate of the inverter, a drain capacitor connected to the drain of the inverter, and a gate capacitor connected to the gate of the inverter. A feedback resistor connected between the drain and the gate, a gate pad connected to the gate of the inverter, a drain pad connected to the drain of the inverter, a piezoelectric vibrator connected to the gate pad and the drain pad, and a piezoelectric vibrator connected to the gate pad and the drain pad of the inverter. An oscillation circuit is constituted by an optional resistor whose one end is connected to the gate or drain, and an optional pad which is connected to the other end of the optional resistor.

[0008]

[Operation] By combining the connection between the optional pad connected from the gate or drain of the inverter via the optional resistor and the piezoelectric vibrator, the feedback resistor and the optional resistor connected to the optional pad are connected in parallel, and the inverter The actual feedback resistance between the gate and drain can be varied. If the feedback resistance value is large, the negative resistance will be large on the low frequency side, and conversely, if the feedback resistance value is small, the negative resistance will be large on the high frequency side, so when the oscillation frequency is low, the option pad is not connected and the The oscillation conditions are optimized by increasing the feedback resistance value and, when the oscillation frequency is high, by connecting an optional pad to reduce the actual feedback resistance value. This allows one oscillation circuit, especially one oscillation circuit IC, to oscillate over a wide frequency range.

[0009]

[Examples] Examples of the present invention will be described below. FIG. 1 is a circuit diagram showing an embodiment of the present invention, and 1 is a high-speed CMOS inverter that can operate at the highest frequency of the oscillation frequency band. 2 is a gate capacitance connected to the gate of the inverter, and 3 is a drain capacitance connected to the drain of the inverter, each of which also includes capacitances such as stray capacitance of the pattern and parasitic capacitance of the inverter. 4 is a feedback resistor connected between the gate and drain of the inverter, which determines the operating bias of the inverter and also has the property of determining the oscillation frequency band. 5 is a gate pad connected to the gate of the inverter, 6 is a drain pad connected to the drain of the inverter, and each pad is connected to an external piezoelectric vibrator 7 by wire bonding or the like. 8 is an output buffer that amplifies and outputs the oscillation waveform. A first optional resistor 9 has one end connected to the gate of the inverter, and the other end connected to the optional pad 10. 11 is 9
Similarly, the second optional resistor has one end connected to the gate of the inverter, and the other end connected to the optional pad 12.

In the oscillation circuit configured as described above, the feedback resistor 4, first optional resistor 9, and second optional resistor 11 are set as shown in Table 2 below, by way of example.

[Table 2] In order to cause the above oscillation circuit to oscillate over a wide frequency band, the first and second optional resistors are used for each frequency band as shown below based on FIG. First, at low frequencies, only the gate pad 5 and drain pad 6 are connected to both terminals of the piezoelectric vibrator and operated. Next, at the intermediate frequency, in addition to the gate pad and the drain pad, the optional pad 10 or 12 of either the first optional resistor or the second optional resistor is connected to the piezoelectric vibrator terminal on the side connected to the drain pad 6. . As a result, the feedback resistor and the first or second optional resistor are connected in parallel, the actual feedback resistance value decreases, and the oscillation frequency band shifts to the high frequency side. At the next highest frequency, in addition to the gate pad and the drain pad, the optional pads 10 and 12 of both the first and second optional resistors are connected to the piezoelectric vibrator terminal on the side connected to the drain pad 6. As a result, the actual feedback resistance value further decreases, and the oscillation frequency band shifts to a higher frequency side.

As an example, when the oscillation circuit of this embodiment is operated from 5 MHz to 75 MHz, the optional pads and the piezoelectric vibrator are connected by wire bonding or the like as shown in Table 3.

[Table 3] As described above, it is possible to optimize the oscillation conditions by changing the actual feedback resistance value according to the oscillation frequency band, so one oscillation circuit or one oscillation IC can handle a wide frequency band. It can be covered.

In this embodiment, one ends of the first and second optional resistors are connected to the gate of the inverter.
A similar effect can be achieved with a configuration in which the inverter is connected to the drain of the inverter as shown in FIG.

Furthermore, in this embodiment, two optional resistors are connected, but the same effect can be obtained even if one optional resistor or three or more optional resistors are used. It will be done.

In addition, in this embodiment, the resistance value feedback resistor is 2MΩ, the first option resistance is 6KΩ, and the second option resistance is 2MΩ.
The optional resistance was set to 4KΩ to enable oscillation operation over a wide range, but in the second embodiment, the feedback resistance was set to 5KΩ, the first option resistance was 100KΩ, and the second option resistance was 50KΩ. If you connect the optional pads as shown in , the actual feedback resistance values will be 5KΩ, 4.7KΩ, 4.5KΩ, 4.
It is possible to change the resistance value within a small width of 3KΩ. By doing this, the IC built-in resistance is generally ±10 to 20% in mass production.
Although there is a degree of variation, it is also possible to correct this variation and optimize the oscillation conditions to achieve stable oscillation.

[0015]

[Effects of the Invention] According to the present invention, the substantial feedback resistance can be varied by arbitrarily combining the connection between the option pad and the piezoelectric vibrator. ICs can cover a wide frequency band under optimal oscillation conditions. Furthermore, it is possible to configure a configuration that corrects mass-produced variations in feedback resistors, so oscillation conditions can be optimized and stable oscillation can be achieved.

[Brief explanation of drawings]

FIG. 1 is an oscillation circuit diagram showing one embodiment of the present invention.

FIG. 2 is a wire bonding diagram showing a connection method according to an embodiment of the present invention.

FIG. 3 is an oscillation circuit diagram showing another embodiment of the present invention.

FIG. 4 is a negative resistance characteristic diagram showing changes in negative resistance value due to feedback resistance value.

FIG. 5 is an oscillation circuit diagram showing an example of a conventional oscillation circuit.

[Explanation of symbols]

1, 101 Inverter 2, 102 Gate capacity 3, 103 Drain capacity 4, 104 Feedback resistance 5, 105 Gate pad 6, 106 Drain pad 7, 107 Piezoelectric vibrator 8, 108 Output buffer 9 First option resistance 10, 12 Option pad 11 Second optional resistor

Claims (1)

[Claims] Claim 1: An inverter, a gate capacitor connected to the gate of the inverter, a drain capacitor connected to the drain of the inverter, a feedback resistor connected between the drain and gate of the inverter, and a feedback resistor connected to the gate of the inverter. a drain pad connected to the drain of the inverter, a piezoelectric vibrator connected to the gate pad and drain pad, an optional resistor whose one end is connected to the gate or drain of the inverter, and the optional resistor. An oscillator circuit comprising an optional pad connected to one end of the other end.