JPS5934725A - Waveform shaping circuit - Google Patents

Abstract

PURPOSE:To obtain a waveform shaping circuit which converts a sine wave into a rectangular wave of accurate 50% duty, by using a voltage source which is common with the bias voltage of an input signal and the reference voltage, and making an AC signal coincident with the center of the reference voltage. CONSTITUTION:A DC constant voltage power supply 30 is formed by applying the voltage obtained by dividing a power supply 10 into the center value between the high and low level output voltages of a comparator 1 via resistances 3 and 4 to an operational amplifier 9 which functions as a buffer. An input signal is supplied to an input terminal 21, and the DC component is eliminated by a capacitor 2. Thus the input signal is turned into an AC signal which is set by the resistances 3 and 4. The reference voltage which is decided by resistors 3, 4, 7 and 8 and the high and low level output voltages of the comparator 1 is compared with the above-mentioned AC signal by the comparator 1. Thus a rectangular wave of an accurate 50% duty is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waveform shaping circuit, and more particularly to a waveform shaping circuit that converts a sine wave or an input signal close to a sine wave into an accurate 50% duty rectangular wave.

A conventional circuit of this type is shown in FIG. In the figure, (2) is a capacitor that removes the DC component of the input signal, (3) and 14) are resistors, which are connected in series with each other and inserted between the power supply (Il) and the ground. ) applies a bias voltage to the input signal from which the current component has been removed. (5) is a resistor, and the input signal to which the bias voltage has been applied by resistors (3) and (4) is applied to the input signal of the comparator (1). Transfer to negative input terminal.+6
1. +7+, +8) are resistors, one terminal of which is connected to each other and connected to the positive input terminal of the comparator (11), and the other terminal is connected to the power supply 0α,
Connected to ground and the output terminal of the comparator (1). Also, the 't sister ton mentioned above is a power supply for a constant voltage circuit, and c! 1) is an input terminal, and 1) is an output terminal.

Next, the operation of this circuit will be explained. Input terminal C?
The input signal to 11 has its direct and L components removed by a capacitor (2), and becomes an alternating current signal whose center is the bias voltage set by resistors (3) and (4).

The comparator (1) converts the AC signal into a rectangular wave by comparing this AC signal with the reference voltage applied to the positive input terminal, but the resistor (8) provides hysteresis. Therefore, due to this hysteresis, 2
It is necessary to set the center value of the reference voltage that takes the value to the aforementioned bias voltage. If you set it as above,
When this circuit inputs a sine wave as an input signal, it is possible to convert it into an accurate 5 (1% tutee) square wave. Since it is necessary to match the center candy, it is necessary to adjust the resistance value or use a high-precision resistor.

This invention was made to eliminate the drawbacks of the conventional circuit as described above, and by using a DC constant voltage power supply and using this voltage as the bias voltage of the input signal and the center voltage of the reference voltage, It is an object of the present invention to provide a waveform shaping circuit that can convert a sine wave into an accurate rectangular wave with a 5° amplitude without depending on the precision of the resistor.

An embodiment of the present invention will be described below with reference to the drawings. Second
The figure shows an actual TM using an operational amplifier as a DC constant voltage power supply.
Indicates fylr. In the figure, (2) is condensate? -, one electrode is connected to the input terminal (2]), and the other electrode is connected to the negative input terminal of the comparator (1). (3) and (4
) are resistors connected in series and inserted between the power supply (10) and the ground. (9) is an operational amplifier, which is used as a buffer by connecting the negative side input terminal and output terminal, and the operational amplifier (9) and the resistor +
31 +41 constitutes a DC constant voltage power supply measurement. The positive input terminal of the operational amplifier (9) is connected to the connection point between the resistors t31 and +41, and to the -s unity point. (5) is a resistor inserted between the output terminal of the operational amplifier (9) and the connection point of the negative input terminal of the capacitor (2) and the comparator (1).
The output voltage of the DC constant voltage power supply GO+ is applied as a bias voltage to the input signal from which the current component has been removed by 2(.
9) and the positive input terminal of the comparator (1), and between the positive input terminal and the output terminal of the comparator (1). It constitutes a reference voltage creation circuit (31) that creates a reference voltage for the comparator (1) which takes two values due to hysteresis by sandwiching the output voltage of the power supply ((O). Also, the power supply aα is a constant voltage circuit. There is a power supply, and lA is the output terminal.

Next, the operation of this circuit will be explained.

The human input signal to the input terminal (threshold) has the @ current component removed by the condenser (2), and becomes an alternating current o1 signal whose center value is the bias voltage set by the resistor i31141. Comparator (1) performs waveform shaping by comparing this alternating υl'L signal with the reference voltage applied to the positive input terminal.The reference military resistor (31141 (71!
8) and the no-i level output pressure of comparator (1),
Determined by low level output voltage.

Here, if the resistor [determined by 31+41] and the bias voltage are set directly at the center 1 of the high-level output voltage and low-level output voltage of the comparator (1), the reference voltage will be centered at the bias voltage. Take the binary voltage. Therefore, since the center of the AC signal and the center of the reference voltage match, it is possible to convert a sine wave input signal into an accurate 50% square wave with 5J capability. In this embodiment as well, if the voltage of the resistor +31141 changes, the center of the AC signal will always be within the hysteresis of the reference voltage. Therefore, the dependence of the resistor on the third degree is much lower than in the conventional circuit shown in FIG.

As described above, according to the present invention, lj:, [nine constant + tj
13:: Bias the output voltage of the power supply to the input signal "GU-"
At the same time, this DC constant K EE [ti!
By using hysteresis to create a reference voltage for a comparator that takes two values, the dependence on the accuracy of the resistor can be kept very low, making it possible to obtain a highly accurate waveform shaping circuit. be.

[Brief explanation of the drawing]

The first factor is a circuit diagram showing a waveform shaping circuit of 71 meters, and FIG. 2 is a circuit diagram showing an example of the present invention. In the figure, (1) is a comparator, tJOl is a blood flow constant voltage 1 source, and (jl) is a base $4 pressure 1 circuit. shows. Agent IH Kuzuno

Claims (1)

[Claims] (1) A converter converter that has hysteresis and converts the input signal into a rectangular wave by comparing the reference voltage and the input signal, and a DC constant voltage power supply that applies the output voltage to the input signal as a bias voltage; 1. A waveform shaping circuit comprising: a reference voltage creation circuit for creating the reference voltage of the comparator that takes an output voltage of a DC constant voltage power supply and takes two values due to hysteresis.