JPH0629796A - Waveform shaping circuit - Google Patents

Abstract

PURPOSE:To prevent the variation of the duty of a square wave output regardless of the variation of the amplitude of an input signal by connecting the amplitude control circuit to limit an output signal to a certain level. CONSTITUTION:The amplitude control circuit, consisting of a resistance R2, diodes D1 and D2 connected in parallel in opposite directions, and a capacitor C2 is connected to the output of an inverting amplifier 11 for the purpose of limiting the input signal amplitude of an inverting amplifier 11 in the next stage to a certain level. That is, almost all of distortion of the output signal of the amplitude control circuit is eliminated whether the amplitude of the input signal is large or small. The extent of distortion to be eliminated is determined by the input signal amplitude, the gain of the inverting amplifier I1, and the limit level of the amplitude limiting circuit, and it is sufficient if the amplitude limit level is sufficiently lower than the output level of the inverting amplifier I1. Consequently, the duty of the square wave signal obtained by shaping the output waveform of the amplitude limiting circuit by the inverting amplifier I2 is not affected by the amplitude of the input signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform shaping circuit.

[0002]

2. Description of the Related Art In a conventional waveform shaping circuit, as shown in FIG. 3, a sinusoidal input signal supplied to an input terminal 1 is supplied to an input end of an inverting amplifier I1 via a capacitor C1 and is inverted and amplified. It At this time, the input DC bias voltage of the inverting amplifier I1 is determined by the output of the inverting amplifier I1 being fed back to the input terminal of the inverting amplifier I1 via the resistor R1 which constitutes the feedback circuit.

The output of the inverting amplifier I1 is supplied to the inverting amplifier I2 connected in series and shaped so that its rising and falling edges have a rectangular waveform. Then, a rectangular wave signal is output from the inverting amplifier I2. FIG. 4 shows the signal waveform of each part of the conventional waveform shaping circuit shown in FIG. Figure 3
(A) shows the input signal, and the solid line and the dotted line respectively show the case where the signal amplitude is small and the case where the signal amplitude is large.

Although not shown in the figure, the inverting amplifier I1 usually has a structure in which P-channel and N-channel MOS transistors are connected to each other. It is an amplifier. Therefore, the output waveform of the inverting amplifier I1 is distorted as shown by a solid line and a dotted line in FIG. 3B depending on whether the input amplitude is small or large.

On the other hand, the DC bias voltage generated at the input of the inverting amplifier I1 coincides with the output voltage of the inverting amplifier I1 when there is no signal. However, when there is a signal, the output signal of the inverting amplifier I1 is fed to the capacitor C1 and the resistor R1.
In FIG. 4B, when the input has a small amplitude, the level is stabilized at a level L1 where the upper and lower surface responsibilities are equal.

At this time, there is no problem if the inverting amplifier I1 has a linear characteristic, but in reality, since it has a non-linear characteristic as described above, a DC bias voltage generated at the input of the inverting amplifier I1 when the input has a large amplitude. Is stabilized at a level L2 lower than the level L1 as shown in FIG. 4B, as a level such that the upper and lower surface responsibilities are equal.

That is, the DC bias voltage generated at the input of the inverting amplifier I1 varies depending on whether the input signal amplitude is small or large. Therefore, the rectangular signal obtained by waveform-shaping the output of the inverting amplifier I1 by the inverting amplifier I2 has different pulse widths depending on whether the input signal amplitude is small or large, as shown by the solid line and the dotted line in FIG. 4C. . That is, when the amplitude of the input signal changes, the duty also changes.

[0008]

In this conventional waveform shaping circuit, the duty of the rectangular wave signal whose waveform has been shaped varies due to the variation of the input signal amplitude. In other words, there is a problem that jitter is generated, which causes noise to a circuit (not shown) connected to the next stage.

An object of the present invention is to provide a waveform shaping circuit in which the duty of a rectangular wave output does not change even if the input signal amplitude changes.

[0010]

A waveform shaping circuit according to a first aspect of the present invention includes a first inverting amplifier for connecting a sinusoidal input signal to an input terminal via a first capacitor, and the first inverting amplifier. A feedback circuit for feeding back the output of the inverting amplifier to the input side, an amplitude limiting circuit for removing distortion of the output of the first inverting amplifier and inputting it to the second inverting amplifier, and an output of this amplitude limiting circuit And a second inverting amplifier that produces a square wave signal.

A waveform shaping circuit according to a second aspect of the present invention includes a resistor having one end connected to the output of the first inverting amplifier and the other end connected to the input of the second inverting amplifier, and a reciprocal polarity. Has an amplitude limiting circuit in which one ends of a first diode and a second diode connected in parallel with each other are connected to an input of the second inverting amplifier, and the other end is connected to a reference power source through a second capacitor. .

In the waveform shaping circuit of the third aspect of the present invention, a resistor is used in the feedback circuit.

[0013]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention.
In this embodiment, the output of the inverting amplifier I1 is connected to the resistor R2 and the diodes D1 and D2 connected in parallel in the opposite direction so as to limit the input signal amplitude of the inverting amplifier I2 at the next stage to a constant level.
And an amplitude control circuit including a capacitor C2 are connected.

When the input signal amplitude is small or large as shown by the solid and dotted lines in FIG. 2A, the output of the amplitude limiting circuit is almost distorted as shown by the solid and dotted lines in FIG. 2B. To be removed. The amount of distortion to be removed is determined by the input signal amplitude, the gain of the inverting amplifier I1, the limiting level of the amplitude limiting circuit, etc., and the amplitude limiting level may be sufficiently lower than the output level of the inverting amplifier I1. Therefore, the duty of the rectangular wave signal obtained by shaping the output waveform of the amplitude limiting circuit by the inverting amplifier I2 is not affected by the amplitude level of the input signal as shown in FIG.

[0015]

As described above, according to the present invention, the duty of the shaped rectangular wave signal is not affected by the variation of the amplitude level of the input signal. That is, there is an effect that jitter does not occur.

[Brief description of drawings]

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

FIG. 2 is a signal waveform diagram of each part of FIG. 1, where (a) shows an input signal, (b) shows a signal waveform after amplitude limitation,
(C) is a figure which shows the rectangular-wave signal after waveform shaping.

FIG. 3 is a block diagram of a conventional waveform shaping circuit.

4A and 4B are signal waveform diagrams of respective parts of FIG. 3, in which FIG. 4A shows an input signal, FIG. 4B shows an output waveform of the inverting amplifier I1, and FIG. 4C shows a rectangular wave signal after waveform shaping. Is.

[Explanation of symbols]

 1 Input Terminal 2 Output Terminal 3 Feedback Circuit C1, C2 Capacitor R1 Resistor D1, D2 Diode I1, I2 Inverting Amplifier

Claims (3)

[Claims] 1. A first inverting amplifier that connects a sinusoidal input signal to an input terminal via a first capacitor, a feedback circuit that feeds back the output of the first inverting amplifier to an input side, and 1 has an amplitude limiting circuit for removing the distortion of the output of the inverting amplifier and inputting it to the second inverting amplifier, and the second inverting amplifier for inputting the output of this amplitude limiting circuit to generate a rectangular wave signal. A characteristic waveform shaping circuit. 2. A resistor, one end of which is connected to the output of the first inverting amplifier and the other end of which is connected to the input of the second inverting amplifier, and a first diode and a second diode which are connected in parallel in opposite polarities. 2. The waveform according to claim 1, further comprising an amplitude limiting circuit in which one end of the diode is connected to an input of the second inverting amplifier, and the other end is connected to a reference power source through a second capacitor. Shaping circuit. 3. The waveform shaping circuit according to claim 1, wherein a resistor is used in the feedback circuit.