JPS61190672A - Integrator - Google Patents

Abstract

PURPOSE:To obtain an integrator of small integration output voltage drift against fluctuation of temperature of a circular or fluctuation of power source voltage by leading middle point voltage of an inversion and a non-inversion signal to an input terminal of a differential amplifier circuit as a reference signal. CONSTITUTION:An input pulse signal is waveform shaped by a D type flip-flop 11, and the non-inversion output signal Q is inputted to an integrating circuit 12 to find an integration value. The integration value is further inputted to an inversion input terminal of an operational amplifier 15. Middle point voltage between a non-inversion output signal Q and an inversion output signal Q' is inputted to another non-inversion input terminal of the operational amplifier 15 as a reference signal, and the operational amplifier 15 amplifies and outputs the integration value from the integrating circuit 12 making the middle point voltage a basis. At this time, even if the inputted non-inversion output signal Q causes fluctuation of level, the middle point voltage fluctuates by the same amount, and fluctuation of level is canceled by the operational amplifier 15.

Description

[Detailed Description of the Invention] [Summary] This relates to an integrator that calculates the difference between the voltage obtained by integrating one of an inverted signal and a non-inverted signal obtained from an input pulse signal and the midpoint voltage of both signals. By outputting from a differential amplifier circuit, an integrator with less output voltage drift caused by temperature fluctuations, power supply voltage fluctuations, etc. is realized.

[Industrial application field]

The present invention relates to an integrator. The integrator of the present invention can be applied to, for example, an integrating circuit of a transversal equalizer used in a digital communication system.

In a transversal equalizer, an integrator is used as a correlator for determining tap coefficients, and an integrator with a small output voltage lift is desired.

[Conventional technology]

A conventional general integrator is shown in FIG. The conventional integrator includes a time constant circuit consisting of a capacitor C20 and a resistor R20 in the output feedback circuit of the operational amplifier 21. In this integrator, a pulse signal whose duty ratio changes is inputted via the resistor R21, and an integrated output value of an analog quantity is outputted, so that the integrated output value becomes zero when the duty ratio is 50%. Offset adjustment is performed with variable resistor VR20.

[Problem that the invention seeks to solve]

The integrator shown in FIG. 4 has a problem in that if the input signal level drifts due to ambient temperature fluctuations or power supply voltage fluctuations, this will directly appear as a drift in the integrator output voltage.

Therefore, it is an object of the present invention to provide an integrator with less integrated output voltage drift even with circuit temperature fluctuations or power supply voltage fluctuations.

Measures for solving problem C] In order to solve the above problem, as shown in Figure 1,
A circuit 1 that creates an inverted signal and a non-inverted signal of an input pulse signal, an integrating circuit 2 that integrates one of the inverted signal and the non-inverted signal, a circuit 3 that extracts the midpoint voltage of the inverted signal and the non-inverted signal, An integrator is provided which includes a differential amplifier circuit 4 to which the integrated output signal of the integrating circuit and the midpoint voltage signal of the cough removal circuit are respectively input.

[For production]

One of the inverted signal and the non-inverted signal of the input pulse signal is integrated by an integrating circuit 2 to obtain an integral value. This integral value will be amplified by the differential amplifier circuit 4, but since the differential amplifier circuit has one input terminal led to the midpoint voltage of the inverted and non-inverted signals as a reference signal, the input pulse signal Even if a voltage level drift occurs due to temperature fluctuations or power supply voltage fluctuations, the reference signal also drifts, and eventually these drifts are canceled out by the differential amplifier circuit 4 when averaged over time. It does not appear in the final integrated output signal.

〔Example〕

An integrator according to one embodiment of the invention is shown in FIG.

In FIG. 2, a pulse signal whose duty ratio is variably controlled is input to the D input terminal of the D-type flip-flop 11. The D-type flip-flop 11 outputs between a non-inverted output signal Q and an inverted output signal, and the non-inverted output signal Q is led to an inverted input terminal of an operational amplifier 15 via an integrating circuit 12.

Moreover, the midpoint voltage between the non-inverted output signal Q and the inverted output signal is determined by resistor voltage dividers R1 and R2 (R1=R2), and this midpoint voltage is offset adjusted by connecting one end to the ground or reference voltage. The signal is guided to the non-inverting input terminal of the operational amplifier 15 as a reference signal via the variable resistor VRI. FIG. 4 shows the waveform between the non-inverted output signal Q and the inverted output signal. As you can see from this waveform diagram, the midpoint voltage has two waveforms Q...! : At the point where T intersects, for example, when the input signal is at TTL level, the dynamic voltage is approximately half of the TTL level.

The operational amplifier 15 works as a differential amplifier circuit,
A feedback resistor R3 is connected and its output signal becomes the final integrated output signal of the integrator.

In the device shown in FIG. 2, the integration constant of the integrating circuit 12 and the offset level by the variable resistor VRI are adjusted so that the output signal of the operational amplifier 15, that is, the integrated output signal becomes zero when the duty ratio of the input pulse signal is 50%. is adjusted.

The operation of the FIG. 2 apparatus will now be described.

The input pulse signal is reshaped and waveform-shaped by the D-type flip-flop 11, and its non-inverted output signal Q is sent to the integrating circuit 1.
2 to obtain an integral value, and the integral value is further input to one inverting input terminal of the operational amplifier 15.

Since the midpoint voltage between the noninverting output signal Q and the inverting output signal is input as a reference signal to the other non-inverting input terminal of the operational amplifier 15, the operational amplifier 15 performs an integration circuit using this midpoint voltage as a reference. The integrated value from 12 is amplified and output.

Now assume that the voltage level of the input pulse signal has changed due to temperature fluctuations around the device or power supply voltage fluctuations. Then, the voltage levels between the non-inverted output signal Q and the inverted output signal shown in FIG. 5 either rise or fall in accordance with the level change. The same applies to the midpoint voltage.

Therefore, as the voltage level of the input signal changes, the level of the non-inverted output signal Q input to the integrating circuit 12 will change, but since the midpoint voltage will also change by the same amount, this level change will occur over time. When averaged over , it is canceled out by the operational amplifier 15 and does not appear in the final integrated output signal of the integrator.

Various modifications can be made in carrying out the invention. For example, in the second embodiment, a D-type flip-flop is used as a circuit for obtaining inverted and non-inverted output signals of the input pulse signal, but the invention is not limited to this, and for example, the input pulse signal can be split into two and one of the two is used. It is also possible to use a circuit that uses an inverter. Further, in the same embodiment, the non-inverted output signal of the input pulse signal is inputted to the integrating circuit, but it is of course possible to input the inverted output signal.

Furthermore, in order to have a limiter effect on the output voltage of the operational amplifier, a diode D as shown in the integrator 14 in FIG.
By connecting a circuit consisting of Dt, resistors R4 and R5 in parallel to resistor R3, it is possible to provide limiter characteristics as shown in FIG.

A specific application example of the integrator according to the present invention is shown in FIG. The device shown in FIG. 6 is a transversal equalizer used in a digital communication system using a multilevel orthogonal amplitude modulation method.

In FIG. 6, the block represented by the symbol T is an analog delay line, Σ is a sum amplifier, DEC is an identification circuit,
FF is a flip-flop, SR is a shift register as a delay element, and the exclusive OR circuit in the figure works as a correlator. The block denoted by the symbol f is an integrator according to the present invention, and its integral output signal controls the coefficients of the corresponding multiplier on the left side of the drawing.

〔Effect of the invention〕

According to the present invention, even if the input digital signal drifts due to temperature fluctuations in the device or power supply voltage fluctuations,
Voltage drift in the final integrated output signal is significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a principle block diagram of the present invention, Fig. 2 is a circuit diagram of an integrator as an embodiment of the present invention, Fig. 3 is a limiter characteristic diagram according to the present invention, and Fig. 4 is a diagram of a conventional integrator. 5 is a diagram of the D-type rough flip-flop output waveform in the device shown in FIG. 2, and FIG. 6 is a block diagram of a transversal equalizer to which the integrator of the present invention is applied. 1... Inverting/non-inverting signal generation circuit, 2.12... Integrating circuit, 3.13... Midpoint voltage generation circuit, 4.14... Differential amplifier circuit, 11... D type Flip-flop, 21, 31... operational amplifier. Fig. 1 Block diagram of the principle of the present invention 30 lJ transmitter characteristics diagram according to the present invention

Claims (1)

[Claims] 1. A circuit (1) that creates an inverted signal and a non-inverted signal of an input pulse signal, an integrating circuit (2) that integrates one of the inverted signal and the non-inverted signal, the inverted signal and An integrator comprising: a circuit (3) for extracting a midpoint voltage of a non-inverted signal; and a differential amplifier circuit (4) to which an integral output signal of the integrator circuit and a midpoint voltage signal of the retrieving circuit are respectively input. vessel.