JPS6156506A - Signal output circuit - Google Patents

Abstract

PURPOSE:To reduce a delay of sigal transmission and to prevent te generation of head with an internal element of a drive circuit, by supplying the output of a 1-shot circuit to the control terminal of a switching element and putting the switching element under a conduction state while signals are delivered from the 1-shot circuit. CONSTITUTION:When a signal Sa to be trasmitted is changed to a low level from a high level, the pulse of the fixed time width (t) is delivered from a 1-shot circuit 12. Then a transistor TR1 is set ON for an extremely short time. Thus a large current is supplied to a trasmisson line L for a short time via a resistance R3 and the TR1. Then, the electrostatic capacity of the line L and a capacitor C1 are charged in a short time. As a result, the potential Vb of the input terminal of a buffer 11 is set at a high level with an extremely short time delay from the fall of the signal Sa. This can reduce greatly the transmission delay of signals and then decrease the power consumption of both the R3 and the TR1.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a system in which a signal to be transmitted is supplied to an input terminal of a drive circuit constituted by an integrated circuit, and an output terminal of this drive circuit is connected to a transmission line. This invention relates to a signal output circuit.

<Prior Art> As shown in FIG. 3, a conventional signal output circuit that outputs a digital signal to a transmission line supplies a signal to be transmitted to an input terminal 10a of a drive circuit 10 made of an integrated circuit, and The output terminal 10b of the integrated circuit 10 is connected to one end of the transmission line L. The other end of the transmission line L is connected to the input terminal 1) of a buffer 1) for signal reception.
a, a pull amplifier resistor R1 is connected between this other end and the power supply line PL, and a capacitor C1 is connected between the other end and the ground.

<Problems to be Solved by the Invention> In such a conventional system, due to the influence of the capacitance of the capacitor CI provided for noise absorption and the transmission line L, as shown in Fig. 4+a) and Tbl. There is a delay in the change in the potential vb at the input terminal of the buffer 11 with respect to the fall of the input signal Sa, resulting in a problem that the signal transmission speed becomes slow.

In order to eliminate this problem, the pull amplifier resistor R1 can be made smaller to shorten the charging time constant. However, if this is done, when the output terminal 10b of the drive circuit 10 is at a low level, the resistor R1 The current flowing through the drive circuit 10 increases, which not only causes an increase in power consumption, but also increases heat generation in the internal circuit of the drive circuit 10, which may shorten the life of the drive retreat path 10.

Means for Solving the Problems> The present invention provides a means for solving the above problems.
A resistor and a semiconductor switching element are connected in series, and in response to a change in the state of a signal input to the drive circuit, a signal is generated for a certain period of time from the point at which the output of the drive circuit starts changing from a low level to a high level. A one-shot circuit is provided to output the one-shot circuit, and the output of the one-shot circuit is supplied to the control terminal of the switching element to output the one-shot circuit.
The present invention is characterized in that the switching element is kept conductive while a signal is being output from the node circuit.

When the state of the input signal changes in the direction in which the output of the drive circuit changes from a low level to a high level, in response, a pulse with a fixed time width is output from the one-shot circuit, and the amount rate of this fixed time The conductor switching element becomes conductive. As a result, the capacitance of the transmission line and the capacitor on the receiving circuit side are rapidly charged, the rising speed of the potential on the receiving side is accelerated, and the delay in signal transmission is reduced.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, circuit components that are the same as the conventional ones are given the same reference numerals as in FIG. C1 indicates a capacitor.

In this configuration, the present invention connects the resistor R3 and the NPN transistor constituting the semiconductor switching element in series between the output terminal 10b of the drive circuit 10 and the power supply line PL, and also connects the resistor R3 and the NPN transistor constituting the semiconductor switching element in series. A one-shot circuit 12 that outputs a pulse sb with a constant time width t in response to a change in the signal Sa input to the drive circuit 10 from high level to low level is connected to the drive circuit 10, and the output of this one-shot circuit 12 is is configured to be supplied to the base of the transistor TRI.

Note that the value of the resistor R3 is determined by the capacitance of the transistor TRI, etc., and a resistor R3 having a smaller resistance value than the resistor R1 is selected.

In a circuit having such a configuration, when the signal state of the signal Sa to be transmitted changes from a high level state to a low level state as shown in FIG. As shown in FIG. 2(b), a pulse with a constant time width t is output, and the transistor TR1 is turned on for a very short time. As a result, the transmission line L
A large current is supplied in a short time through the resistor R3 and the transistor TRI, and the capacitance of the transmission line L and the capacitor C1 are charged in a short time. As a result, buffer 1
As shown in FIG. 2 (C1), the potential Vb at the input terminal of the signal Sa becomes high level with a short time delay (as shown in C1 in FIG. 2), and the signal transmission delay can be greatly reduced.

In addition, the transistor TRI is not always on when the signal 3a is at a low level;
As shown in b), since the signal Sa remains on for a certain period of time t immediately after changing from high level to low level, there is an advantage that the power consumption in the resistor R3 and the transistor TRI can be reduced.

Note that an element such as a field effect transistor may be used as the semiconductor switching element.

<Effects of the Invention> As described above, in the present invention, a resistor and a semiconductor switching element are connected in series between the output terminal of a drive circuit constituted by an integrated circuit and a power supply line, and a A one-shot circuit is provided that outputs a pulse with a fixed time width at the timing when the output changes from low level to high level, and the semiconductor switching element is made conductive by the output of this one-shot circuit, thereby reducing power consumption. This method has the advantage that the signal transmission delay in the transmission line can be significantly reduced without increasing the signal speed, and the heat generation of the internal elements of the drive circuit can also be prevented from increasing.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is an overall configuration diagram of a signal transmission circuit, FIG. 2 is a timing chart for explaining the operation of the circuit in FIG. 1, and FIG. 3 and 4 show the prior art. FIG. 3 is an overall configuration diagram of a transmission circuit, and FIG. 4 is a time chart showing its operation. 10...Drive circuit, 1)...Buffer, 12...
One-jit circuit, CI...capacitor, L...transmission line, R1, R3...resistor, TR1...transistor.

Claims (1)

[Claims] (1) In a signal output circuit in which a signal to be transmitted is supplied to an input terminal of a drive circuit constituted by an integrated circuit, and an output terminal of this drive circuit is connected to a transmission line, the output terminal of the drive circuit and a power supply line are connected. At the same time, a resistor and a semiconductor switching element are connected in series, and in response to changes in the state of the signal input to the drive circuit, the output of the drive circuit is constant from the point when the output starts to change from low level to high level. A one-shot circuit that outputs a signal for a period of time is provided, and the output of this one-shot circuit is supplied to a control terminal of the switching element to make the switching element conductive while the signal is output from the one-shot circuit. A signal output circuit characterized in that: