JP2002076849A - Oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillator that utilizes a ring oscillator circuit so as to obtain an output with a high oscillated frequency. SOLUTION: The ring oscillator circuit 1 consists of a series connection of an odd number of inverters 11-13 and is self-oscillated by feeding back an output of the inverter 13 of the final stage to the inverter 11 of the 1st stage. A peak detection circuit 2 sequentially extracts each peak among output voltages V1-V3 of the inverters 11-13 and consists of NMOS transistors(TRs) Q1-Q3 connected to each output terminal of the inverters 11-13 to act like a source follower, and a constant current source I1 that is connected in common to the NMOS TRs Q1-Q3 and acts like their common load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator that can obtain a high oscillation frequency by using a ring oscillator.

[0002]

2. Description of the Related Art Conventionally, a ring oscillator is known as an example of an oscillator. In this ring oscillator, logic gates of inverted outputs, such as an inverter, a NAND gate, and a NOR gate, are connected in odd-numbered stages in series, and the output of the last stage is fed back to the first stage and self-oscillates.

[0003]

The conventional ring oscillator oscillates at a period twice as long as the total sum of the average propagation delay times of the logic gates constituting the oscillator. Therefore, the oscillation increases as the number of logic gate stages increases. The frequency will be lower. For this reason, it has been difficult to realize a conventional ring oscillator that can output a high oscillation frequency.

An object of the present invention is to provide an oscillator capable of obtaining an output with a high oscillation frequency by utilizing a ring oscillator.

[0005]

Means for Solving the Problems In order to solve the above problems and achieve the object of the present invention, the inventions according to the first and second aspects are configured as follows. That is, according to the first aspect of the invention, a ring oscillator circuit in which inverters are connected in series in an odd number of stages and the output of the last stage is fed back to the first stage and self-oscillates, and each peak portion of each output of the inverter is sequentially arranged. And a peak detection circuit for extracting.

According to a second aspect of the present invention, in the oscillator according to the first aspect, the peak detection circuit is connected to each output terminal of each of the inverters and operates as a source follower. And a constant current source commonly connected to each transistor. As described above, in the present invention, the peak detection circuit for sequentially taking out each peak portion of each output of the inverter in the ring oscillator circuit is provided. Therefore, by utilizing the ring oscillator, it is possible to obtain an output with a high oscillation frequency. Can be.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an oscillator according to an embodiment of the present invention will be described below with reference to the circuit diagrams of FIGS. As shown in FIG. 1, the oscillator according to this embodiment includes a ring oscillator circuit 1 and a peak detection circuit 2, and takes out an oscillation output from an output terminal 3.

The ring oscillator circuit 1 includes an odd number of inverters 11 to 13 connected in series, and a final-stage inverter 1
The output of No. 3 is fed back to the first-stage inverter 11 and self-oscillates. For example, as shown in FIG. 2, each of the inverters 11 to 13 is connected between an NMOS transistor Q11 that inverts and outputs an input, a constant current source I11 that functions as a load of the NMOS transistor Q11, and a drain of the NMOS transistor Q11 and the ground. And a load capacity CL.

The peak detection circuit 2 includes inverters 11 to 1
3 are sequentially taken out of each of the output voltages V1 to V3 of the inverter 3, and as shown in FIG.
The NMOS transistors Q1 to Q3 are connected to the output terminals 1 to 13 and operate as a source follower, and the constant current source I1 is connected to the NMOS transistors Q1 to Q3 and functions as a common load. .

[0010] More specifically, the inverter 1
The output terminals 1 to 13 are connected to the NMOS transistors Q1 to Q1.
It is connected to each gate of Q3. The sources of the NMOS transistors Q1 to Q3 are commonly connected, and the common connection is grounded via a constant current source I1 and connected to the output terminal 3. Further, the power supply voltage VDD is supplied to each drain of the NMOS transistors Q1 to Q3.

Next, an example of the operation of the oscillator according to the embodiment having such a configuration will be described with reference to the drawings. When the ring oscillator circuit 1 starts self-oscillation, the output voltages V1 to V3 of the inverters 11 to 13 become:
For example, as shown in FIG. 3, the phases are shifted from each other.

The output voltages V1 to V1 of the inverters 11 to 13
V3 is applied to each gate of the NMOS transistors Q1 to Q3.
Each current according to each of the output voltages V1 to V3 flows through Q3, and the total current of these currents flows into the constant current source I1. Each source of the NMOS transistors Q1 to Q3 has
Since the common constant current source I1 is connected, the sum of the currents of the NMOS transistors Q1 to Q3 is equal to the constant current source I1.
Is limited to the current value I1.

As a result, the output terminal 3 of the peak detection circuit 2
The output voltage Vout from is as shown by the solid line in FIG.
A waveform is obtained by sequentially extracting each peak portion of each of the output voltages V1 to V3 of the inverters 11 to 13, and an output having a high oscillation frequency is obtained. As described above, according to this embodiment, the inverter 11 is controlled by the peak detection circuit 2.
13 are sequentially taken out of each of the output voltages V1 to V3, so that the ring oscillator circuit 1
By using the above, an output having a high oscillation frequency can be obtained.

[0014]

As described above, according to the present invention, the peak detecting circuit for sequentially extracting each peak portion of each output of the inverter in the ring oscillator circuit is provided. Therefore, by utilizing the ring oscillator, an output with a high oscillation frequency can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of each inverter of FIG.

FIG. 3 is a voltage waveform diagram showing voltages of respective parts in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ring oscillator circuit 2 Peak detection circuit 3 Output terminal 11-13 Inverter Q1-Q3 NMOS transistor I1 Constant current source

Claims (2)

[Claims] A ring oscillator circuit in which inverters are connected in series in an odd number of stages and an output of the last stage is fed back to the first stage and self-oscillates; a peak detection circuit for sequentially extracting each peak portion of each output of the inverter; An oscillator comprising: 2. The peak detection circuit includes: a plurality of transistors connected to respective output terminals of the respective inverters to perform a source follower operation; and a constant current source commonly connected to the respective plurality of transistors. The oscillator according to claim 1, wherein