JPS6323418A - Output circuit - Google Patents

Abstract

PURPOSE:To obtain a stable output waveform even with a high power voltage by adding an oscillation preventing resistor to a base of the 4th transistor (TR). CONSTITUTION:The oscillation preventing resistor 11 is inserted between a TR 4 and a point 10. In the presence of a through-current flowing from a power supply 7 to a ground 8, the current flows from the emitter of the TR 4 to the base, but since the resistor 11 exists, the potential at the point 10 does not rise. Thus, TRs 1, 2 in the turn-off state from the turn-on are not turned on again, no oscillation is caused and a stable output waveform is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to output circuits, particularly output circuits with a high power supply voltage.

[Conventional technology]

FIG. 2 is a diagram showing a conventional output circuit. In this figure, 1 is the NP that drives the current flowing to the output terminal 9.
N ) transistor (first transistor), 2 is an NPN transistor for supplying its base current to NPN transistor 1
Transistor (second transistor), 3 is output terminal 9
NPN) transistor (which drives the current flowing from
4 is a PNP transistor (fourth transistor) which supplies its base current to the NPN transistor 3; 5 is an NPN transistor 2;
and PNP l- transistor (fifth transistor) for turning on or off the transistor 4, and a constant current source 6 is provided between its collector and the power supply 7. Note that 12 and 13 are resistors, and 8 is a ground.

Next, the operation will be explained. Let us now consider the case where a signal from "L" to "Hl" is input to the base of transistor 5, and transistor 5 is turned from off to on. When transistor 5 is off, the potential at point 10 is Therefore, transistors 2 and 1 are turned on, and the potential of output terminal 9 becomes ``H''. In this state, transistors 3 and 4 are both turned off.

When transistor 5 changes from off to on, transistor 1.2 changes from on to off, and transistor 3.4 changes from off to on. However, since transistors 2 and 4 have different switching speeds, transistor 3 is turned on before transistor 1 is completely turned off.

Here, we are considering an output circuit with a particularly high power supply voltage (! 30 M), so at this time, a very large through current momentarily flows from the power supply 7 to the ground 8. This large current also flows from transistor 4 to transistor 5, but since transistor 5 is normally a transistor that does not have the ability to drive large currents, the potential at point 10 is It had dropped when it was turned on, but it rose again due to this large current. Therefore, the transistors 1 and 2, which were about to turn off from on, also return to the on state.

Here, the potential force at point 10 is higher than that at output terminal 9 (then transistor 3.4 is turned off and transistor 1.2 is about to be turned on, but transistor 5
Since transistor 4 is turned on, transistor 4 is turned on, and as a result, a through current flows through transistor 1.3 again.

After repeating this process, looking at the waveform at output terminal 9, we get
While the transistor 5 is on, that is, the output terminal 9 is “
It oscillates during L. FIG. 3 shows the waveform at terminal 9 of the conventional output circuit in this case.

(Problem to be Solved by the Invention 3) As described above, the conventional output circuit has a problem in that when the power supply voltage is high, oscillation occurs at the "L" portion of the output waveform.

The present invention has been made to solve the above-mentioned problems, and aims to provide an output circuit that can provide a stable output waveform even when the source voltage is high.

[Means for solving problems]

The output circuit according to the present invention is a circuit in which an oscillation prevention resistor 11 is inserted between the transistor 4 and the point 10.

[Effect]

When the output terminal is "L", the conventional circuit would oscillate if the power supply voltage was high, but in this invention, by adding the oscillation prevention resistor 11, a through current flows to the transistor 4. Even if it were, the potential at point 10 would not rise, so oscillation would no longer occur.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows an output circuit according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG.
This is an oscillation prevention resistor provided to prevent the zero potential from rising.

Next, the effects will be explained.

Consider the case where a through current flows from the power supply 7 to the ground 8 in this circuit. Current flows from the emitter to the base of transistor 4, but because of the presence of resistor 11, the potential at point 10 does not rise.

Therefore, the transistor 1. which has changed from on to off state.
2 is never turned on again and no oscillation occurs.

〔Effect of the invention〕

As described above, according to the output circuit according to the present invention, the fourth
Since an oscillation prevention resistor is added to the base side of the transistor, oscillation does not occur even in circuits with high power supply voltages, and a stable output waveform can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an output circuit according to an embodiment of the present invention;
FIG. 2 is a diagram showing a conventional output circuit, and FIG. 3 is a diagram showing an output waveform of the conventional output circuit. In the figure, 1 to 5 are first to fifth transistors, 6 is a constant current source, 7 is a power supply, 8 is a ground, 9 is an output terminal, and 11
is a resistor for preventing oscillation, and 12.13 is a resistor. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) The first NPN type whose collector is connected to the power supply and whose emitter is connected to the output terminal drives the current flowing to the output terminal.
a second NPN transistor whose collector is connected to a power supply and whose emitter is connected to the base of the first transistor and to the output terminal via a resistor to supply the base current of the first transistor; a third NPN transistor whose collector is connected to the output terminal and whose emitter is grounded to drive a current flowing from the output terminal; an emitter is connected to the collector of the third transistor and the collector is connected to the base of the third transistor; a PNP-type fourth transistor that is grounded through a resistor and supplies the base current of the third transistor; a constant current source that supplies the base current of the second and fourth transistors; a fifth transistor of NPN type, the collector of which is connected to the base of the transistor, the emitter of which is grounded, and the signal from the previous stage is input to the base; An output circuit comprising an oscillation prevention resistor that prevents the output circuit from oscillating when the output terminal changes from "H" to "L".