JPS58114629A - Logical gate circuit - Google Patents

Abstract

PURPOSE:To limit a spike current, by providing a resistance into a series circuit of a pull-up transistor and a pull-down transistor. CONSTITUTION:The collector of a phase dividing transistor TRQ1 is set at an H level when a terminal IN is set at an L level. Thus a pull-up TRQ3 is turned on, and an output terminal OUT has the sufficient driving force. When the terminal IN is set at an H level, the TRQ1 and Q2 are turned on to prevent the increment of the power consumption. While an input signal is changing to an H level from an L level, the TRQ2 and Q3 are sometimes turned on at one time. However, a flow of an excessive current is prevented between a power supply and an earth since a resistance Rs is connected between the emitter of the TRQ3 and the collector of the TRQ2.

Description

[Detailed description of the invention] (1) Technique of the invention Minute hand The present invention relates to a drive section of a TTL circuit, and relates to a novel circuit for suppressing spike current during transient periods.Background of the invention TTL circuit is constructed by connecting various elements between the power supply Vco and ground. TTL @ circuits are used in various IC circuits, for example, in address gates of IC memories using TTL circuits, and many address gates may operate with the same tie voltage.However, prior art and problems The drive circuit of the TTL j circuit of the resistor drive lid at point 1m is composed of a phase splitting transistor Q1, an output pull-down transistor Q3, and a drive resistor R1. In this circuit, when the input IN is at L level, IIQI and Q output are turned off, and Vec drives the load connected to the output terminal 0υT via the resistor R1.

In order to increase this drive capability, it is necessary to reduce RI. On the other hand, if RI is small, when the input IN is at H level, Q1#Ql is turned on and the voltage Vcc -'IL+ -Q
m-GND 2-mh411flitl becomes large, resulting in large current consumption, which is not preferable.

As a circuit that solves this problem, there is a drive circuit with an off-buff circuit as shown in FIG. That is, in place of the drive resistor R1 in FIG. 1, an output-capable transistor Qs and diode D are provided as an off-buffer circuit. And when the input IN is L level, the turtle is Qs, D
Only turn on the output terminal 〇[JT
When driving a load that is connected by Km and the power is at IN or H level, Ql, Q1 on, LQI, and D are turned off to prevent the power consumption of the circuit shown in FIG. 1 from increasing.

However, in this circuit, in steady state, one of Qm and Qs is on and the other is off, but when the input IN is L→■
In a transient state in which Qffi and Qm change, a state occurs in which both Qffi and Qm are turned on. At that time, a large spike-like current flows through Vco-Qs-D-Q snow-GND. In particular, as mentioned above, when many address gates generate the spike currents at the same time, the sum of these large currents flows through the power supply pattern, GND pattern, etc. of the package that houses the IC chip on which the TTL circuit is formed. flow,
The Woe level in the IC chip temporarily decreases,
In addition, if a phenomenon in which the GND level increases occurs, it will impede the operation of the TTL circuit. Also, many I
(4) Purpose of the Invention The present invention provides a drive circuit for a TTL lid path with an off-buffer that has low power consumption and excellent drive ability in a constant state. The purpose of the present invention is to provide a circuit that suppresses spike noise under certain conditions.

(5) Structure of the Invention The present invention is controlled by the collector potential of a phase splitting transistor, an outputtable transistor connected to a power supply, and the emitter potential of the phase splitting transistor. In an am gate circuit comprising an output pull-down transistor read from point IIc1a and an output terminal connected to one connection point Kil of both test transistors,
The connection between the output-capable transistor and the connection point
A current limiting resistor is provided to suppress the spike current flowing from the power supply to the ground point via the output pull-down transistor and the output pull-down transistor in the event of overflow.

(6) Embodiment 5 of the invention. $,7gFi This is a circuit diagram showing an embodiment of the present invention, and each embodiment includes outputtable transistors Qs and Q.
A current limiting resistor 8 is provided between the connection point of s and Qm. The off-buffer 7 circuits shown in FIGS. 5 and 6-7 each consist of Qs, Qm, Qs and Qs, and operate in the same way.

That is, in the steady state s, one of a and Q''@Qa is on and the other is off, so the current consumption is small.

In the transient state s where %Ql#QI%/h deviation is also on L& and 11 resistance Rs K Yol Va e -eGND
Because the current welfare is suppressed, a large spike current flows like in the conventional machine. #11 - And when the Q is turned on, the drive capacity of the barrel decreases slightly. If the %EE is at least the same as No. 11 II. 1. By sufficiently suppressing the spike current, it is possible to reduce the current consumption (as in the case of Fig. 1).

For the ILs of this example, approximately Ω was used with a value of 500 to 1.

In the present invention, a filter is provided at the connection point between the silane resistor Q- and QsaQl, but if only to suppress the spike current, the
i1! As shown in IK, it is also conceivable to provide a current limiting resistor between the collector of the transistor QsO and V(1) as shown in FIG.

However, as shown in No. 411, the input 11tT is L→
■When reaching the level, complete connection is likely to occur -1, that is, Qt turns on, the N2 point rises, and by turning on the Q proverb, Vc
A current flows from c-Rm-D-Qs-Ql-GND, and due to the voltage drop across the relatively auspicious resistance (much larger than r in Figure 2), the level of J)Ns drops below the 6N10 level. Become. Then, a forward bias is applied between the base and collector of Qs, and Qs becomes temporarily saturated. As a result, as shown in the figure, the resistance Rs is 11), Ic+, Icm,
Ice current flows.

C+ is a parasitic capacitance connected to the collector of Qa.

C! is the load capacitance connected to the output terminal 0UTK, and the base current Ib of the Q snow becomes insufficient due to the currents Icm and Ics, and the output terminal OUT rises again. As a result, the level of N1 also rises, and Q- becomes unsaturated again. Then, the OUT goes down... and the signal goes off.

Therefore, in the present invention, a current limiting resistor kLs is provided between the output blue transistor Qs and the connection point between Qa and Qs.
(7) Effects of the Invention According to the present invention, it is possible to prevent a large spike current in a transient state of a drive circuit with an off-buff T, which consumes little power in a steady state, and to maintain a stable state. 0 which can obtain the circuit operation

[Brief explanation of the drawing]

1.2.8 is a conventional circuit diagram, FIG. 4kA is a level diagram explaining the operation of FIG. 8, and FIG. 5.6.7 is a circuit diagram showing an embodiment of the present invention. In the figure, QI is a phase division transistor, Qgi1 output pull-down transistor, Qs is an output pull-down transistor, OUT is an output m-channel, and Vc (・ is an i! source.

Claims (1)

[Claims] Controlled by the collector potential of the phase splitting transistor,
An output pull-down transistor controlled by the first emitter of the phase splitting transistor and connected to the ground, and an output terminal connected to the connection point of both transistors. In the #i/1 gate circuit, a current limiting resistor is provided between the output pull-up transistor and the connection point, and the output pull-down transistor and the output pull-down are connected from the power supply during a transient state. A 111j1 gate circuit characterized in that a spike current flowing to the ``'C grounding point via a transistor is suppressed.