JPH03175730A - Output buffer - Google Patents

Abstract

PURPOSE:To prevent a through current occurring when a signal is changed and to suppress the ringing of an output waveform by attaching a transmission gate. CONSTITUTION:When input is changed from power source potential to ground potential, a second pch transistor 3 is turned on, and a second nch transistor 4 is turned off, thereby, a first pch transistor 1 is turned off. At this time, time difference due to the resistance components of a first transmission gate 5 and a second transmission gate 6 and the capacitance component of the gate capacity of a first nch transistor 2 occurs by the first nch transistor 2 is turned on, therefore, no simultaneous turned on state of the first pch transistor 1 and the first nch transistor 2 occurs, and no through current flows when an output signal is changed. Also, the ringing of the output waveform can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an output buffer for controlling the rise time b1 of an output waveform.

[Conventional technology]

FIG. 2 is a circuit diagram of a conventional output bumper.

In the figure, (1) is the first PCH transistor, (
2) is the first nch transistor, (7), (
8) is an inverter. [Problem to be Solved by the Invention] Conventional output buffers were configured as described above, so when the input signal changes, the inverter (7) outputs the output signal, and the output buffer outputs the output signal through the inverter (8). pch transistor +t
>> and b nch transistor (2) turn on at the same time 1 Not only does a through current flow, but also when the output buffer operates at high speed, ringing occurs in the output waveform, causing malfunction of the integrated circuit connected to the next stage. There was a problem with raising the bow.

The present invention has been made to solve the above-mentioned problems, and aims to provide an output buffer that can prevent through current during output buffer operation and suppress ringing of the output waveform.

[Means to solve the problem]

The output buffer according to the present invention has a transmission gate added thereto.

[Effect]

By adding a transmission gate to the output buffer according to the present invention, it is possible to prevent a through current from flowing when a signal changes, and also to suppress ringing.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a @J path diagram of an output buffer showing an embodiment of the present invention.

In FIG. 1, (1) is the first pch transistor, (2) is the first nch transistor, (3) il
: second pch transistor, (4) is second nch transistor
Transistor h (5) is a first transmission gate, (6) is a second transmission gate, and each source and drain electrode of the first transmission gate (5) are the drain electrode of the second pch transistor (3). p and the second translation cart (6
), and each gate electrode is connected to the source and drain electrodes of the TSL pch transistor "1) and the first nch
The source and drain electrodes of the second transmission gate (6) are connected to the drain electrode of the transistor (2).

The drain electrode of the second nch transistor (4) and the source, drain electrode of the first transmission gate (5) are connected to each other, and each gate electrode is connected to the second pch transistor (3) and the second neh transistor (
4) is connected to the gate electrode.

The cover sofa according to the present invention is constructed as described above. 6. It works as described below.

First, when a power supply potential is applied to the input as an initial state, the second pch transistor (3) is in an off state, and the nch transistor (4) is in an on state, and the first pch transistor (1) is in an on state. 1st nch
Since the transistor (2) is in the off state, the power supply potential is outputted.

Next, when the input changes from the power supply potential to the ground potential, the second
pch transistor (3) is on, second nc
h Transistor (4) is in the off state.

The first pch transistor/1)/i is turned off. At this time, in order for the first nch transistor (2) to turn on, the first transmission gate (
5) Also, since there is a time difference due to the resistance component of the second transmission gate (6) and the capacitance component such as the gate capacitance of the first nch transistor (2),
Since the pch transistor (rl) and the first nch transistor (2) are not turned on at the same time,
No through current flows when the output signal changes.

Also, at this time, the potential applied to the gate electrode of the first nech transistor (2) does not change sharply and it takes time for the signal to rise.
The on-resistance of 2) decreases as the signal changes.

As a result, the fall time of the output waveform is short, the fall time is long <fx,a, and the ringing of the output waveform can be suppressed.

Next, when the input changes from ground potential to power supply potential, the second
The pch transistor (3) is off, and the second pch transistor (3) is off.
Since the transistor (4) is turned on, the first nch transistor (2) is turned off. At this time, by the time the first PCH transistor [1] turns on, the resistance valves of the first transmission gate (5) and the second transmission gate (6), and the first PCH transistor [1] ), a time difference occurs due to capacitance components such as gate capacitance, so the first pch
) U/transistor (1) and the first nch transistor (
2) are not turned on at the same time, no through current flows when the output signal changes.

ifc, at this time, the potential applied to the gate electrode of the first PCH transistor (1) does not change sharply and it takes time for the signal to fall.
) becomes smaller as the signal changes. As a result, the rise time of the output waveform becomes longer, and ringing of the output waveform can also be suppressed.

〔Effect of the invention〕

As described above, according to the present invention, since a transmission gate is added, it is possible to prevent a through current from flowing when a signal changes, and also to suppress ringing of an output waveform.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an output bumper showing an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional output bumper. In the figure, 11), (3) is a pch transistor, and (2). (4) is an nch transistor, +5) and +6) are transmission gates, and (71, <8) is an inverter. Note that in Figure 5, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] a first pch transistor, a first nch transistor having a gate electrode electrically connected to the gate electrode of the first pch transistor, a second pch transistor whose respective drain electrodes are interconnected, and an nch transistor; It has a pch transistor and first and second transmission gates configured by interconnecting drain electrodes and source electrodes of the nch transistor, and the drain electrode of the first pch transistor is connected to the gate of the second pch transistor. the drain electrode of the first nch transistor is connected to the gate electrode of the second nch transistor;
Each source and drain electrode of the transmission gate is connected to the drain electrode of the first PCH transistor and the source and drain electrode of the second transmission gate, respectively, and each gate electrode of the first transmission gate is connected to the second transmission gate. connected to the drain electrodes of the pch transistor and the nch transistor, each source drain electrode of the second transmission gate is connected to the drain electrode of the first nch transistor and the source of the first transmission gate, respectively;
An output buffer, wherein the output buffer is connected to a drain electrode, and each gate electrode of the second transmission gate is connected to the gate electrode of the first PCH transistor and the NCH transistor.