JPH03108912A - Output circuit for current switching logic circuit - Google Patents

Abstract

PURPOSE:To obtain an output circuit for a current switching logic circuit capable of improving the driving capability by means of high speed current switching by discharging a current discharged by transistors(TRs) connected in complementary drive through a TR connected separately. CONSTITUTION:An impedance element Z is connected in series between one conductor of a power supply and a 2nd TR Q22. Then a 3rd TR Q26 of the same conduction type as a 1st TR Q21 and driven at a higher driving threshold voltage than the steady-state voltage drop across the impedance element Z is connected in parallel with a 2nd TR Q22 and the impedance element Z. A control terminal of a 3rd TR Q26 connects to a connecting point between the 2nd TR Q22 and the impedance element Z and an input signal inputted from a control terminal of the 1st TR Q21 is outputted from an output terminal Tout. Thus, the driving capability is improved by the quickened current switching and simple circuit constitution is attained.

Description

[Detailed Description of the Invention] [Summary] The present invention improves the drive capability by speeding up current switching with a simple circuit configuration in a current switching control system and circuit output circuit that performs current switching control in a non-saturated manner. Provided is an output circuit for a current switching type logic circuit, which can shorten the discharge time of a steady current consumption flowing from an output terminal and improve drive capability by speeding up current switching. This is a current switching type in which a first transistor and a second transistor are connected in series so as to be driven complementary to each other between two conductors of a power supply, and the connection point is used as an output terminal to control current input and output. In the output circuit of the logic circuit, an impedance element is connected in series between one conductor of the power supply and a second transistor, and has the same conductivity type as the first transistor and has a drive threshold higher than a voltage drop value due to the impedance element. A third transistor driven by a voltage is connected in parallel to the second transistor and the impedance element, and the third transistor is connected in parallel to the second transistor and the impedance element.
A control terminal of the transistor is connected to a connection point between the second transistor and the impedance element, and an input signal input from the control terminal of the first transistor is output from the output terminal.

[Industrial application field]

The present invention relates to an output circuit of a current switching type logic circuit that performs current switching control in a non-saturated manner and improves drive capability by speeding up current switching with a simple circuit configuration.

In recent years, with the increase in the size of computers and the demand for improved measurement accuracy of measuring instruments, saturation type logic circuits that limit the saturation of transistors and increase the number of delay times, and high-speed drive by eliminating the influence of accumulated charge, have been developed. Non-saturated logic circuits have been developed.

In particular, the output circuit of the above-mentioned non-saturated current switching type logic circuit is
It was originally developed with the aim of increasing speed, but due to the significant increase in the scale of integrated circuits (restrictions on power consumption due to thermal limitations and increased output load due to longer signal lines), Current switching control will be delayed,
It is necessary to further increase the speed of the driving capacity.

[Conventional technology]

Conventionally, the output circuit of this type of current switching type logic circuit was
"Analysis and Design of Integrated Circuits", page 186, Motorola Publishing,
There is one disclosed in Japanese Patent Application Laid-Open No. 56-58326 published on April 1, 1971.

In all of these, an emitter-coupled logic circuit (ECL circuit) that operates at high speed is used in a bipolar logic circuit, and a circuit configuration diagram corresponding to this circuit is shown in FIG.

In the figure, an emitter follower section (EF section) 2 that functions as an output circuit of a conventional current switching type logic circuit is connected to a current switch section (C8 section) 1 that supplies a control current, and is connected to the positive conductor of the power supply. (GND) 4 and the negative conductor (VH
)5, first and second transistors Q21 and Q2□ which are driven complementary to each other are connected in series, and for the first and second transistors Q21 and Q22, a third transistor Q23, a diode Q24, Fourth transistor Q25
and a series connection circuit of resistor R21 are connected in parallel, and the output terminal of the diode Q and the base terminal of the second transistor "22 are connected, and the supply current from the current switch section (C8 section) 1 is connected. Each of the first and second transistors Q
input to the base terminal of SQ, and the connection 1 of the first and second transistors Q and Q
22 This is a configuration in which reading points are output as output terminals T.

ut Next, the operation of the conventional circuit will be explained based on the above configuration. First, when an L4H level signal is input to the base of the input transistor Qol of the current switch section (C8 section) 1, the reference side transistor Qo2 is turned OFF, and an H level signal is output as the first and It is input to the base terminal of each third transistor Q SQ , and the first and third transistors Q 1 and Q are in the ON state and 1
23 It becomes. In this state, the second transistor Q22 is
Maintaining the FF state, current is supplied from the output terminal T to the load side and the output terminal u
The signal at t T rises from "L" to "H" and becomes ut.

Next, when the input signal to the base of the input transistor Q01 of the current switch section (C8 section) 1 changes to HL, each of the first and third transistors Q 1 and Q becomes OFF state, and the 2123rd The transistor Q22 is turned on. In this state, 1llll charges accumulated on the load side from the output terminal T are discharged through the second transistor Q22, and the signal at the output terminal T falls to H-+L.

At In this way, the complementary emitter follower section (EF section) 2 increases the output driving capability by transmitting the load signal, and also increases the output driving capability of each of the first and second transistors Q S
By driving Q in a complementary manner, an emitter follower effect can be expected on the falling edge of the output as well as on the rising edge of the output.

[Problem to be solved by the invention]

The output circuit of a conventional current switching type logic circuit was constructed as described above. However, as the degree of integration of integrated circuits has increased, power consumption has become more restricted due to thermal limitations, and the output load has increased due to longer signal lines. The problem is that the steady current consumption continues to flow for a long time, and the current switching operation is delayed, resulting in a reduction in driving ability.

That is, due to the power consumption limit mentioned above, the emitter follower section (E
It is desirable to reduce the steady current consumption of the F part), but in an emitter follower circuit in which the transistors are connected in a complementary manner, the reduction in the steady current consumption is due to the reduction in the steady current consumption in the complementary connected output stage. Since the base pull-down current in the transistor (second transistor Q22) is reduced, the output pull-down ability of the complementary connected lower transistor (second transistor Q22) will be insufficient.

The present invention has been made to solve the above problems, and by discharging the current discharged by the transistors connected to drive complementary to each other by the separately connected transistor, the steady consumption flowing from the output terminal is reduced. It is an object of the present invention to provide an output circuit for a current switching type logic circuit that can shorten the current discharge time and improve the driving ability by speeding up current switching.

[Means to solve the problem]

FIG. 1 is a diagram explaining the principle of the present invention.

In the same figure, a first transistor Q21 and a second transistor Q2 are driven complementary to each other between two conductors of the power supply.
□ are connected in series and the connection point is used as an output terminal T to control current input/output. Z
are connected in series, and a third transistor Q26, which has the same conductivity type as the first transistor Q21 and is driven at a driving threshold voltage higher than the steady state voltage drop value due to the impedance element Z, is connected to the second transistor Q22 and the impedance. The third transistor Q26 is connected in parallel to the element Z, and the control terminal of the third transistor Q26 is connected to the second transistor Q2.
2 and the impedance element Z, and the input signal input from the control terminal of the first transistor Q21 is output from the output terminal T2.

[Effect]

In the present invention, an impedance element is connected to a pair of transistors that are connected to be driven complementary to each other, and a transistor that is driven at a driving threshold voltage higher than the voltage drop value of the impedance element in a steady state is connected in parallel to the transistor. By connecting them, the charges accumulated in the load can be discharged, especially through the discharge paths of the plurality of transistors, and the driving ability can be improved by speeding up current switching, and the circuit configuration can be simplified.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIG. 2.

FIG. 2 shows a configuration diagram of an output circuit of a current switching type logic circuit using bipolar transistors according to this embodiment.

In the figure, the circuit of this embodiment has a current switch section (
It is configured as an emitter follower section (EF section) 2.3 connected to C8 section) 1, and this emitter follower section (EF section) 2 will be explained below.

The lower middle part (EF part) 2 of the emitter fin as the circuit of this embodiment has a positive conductor (GND) 4 and a negative conductor (-V,
, ), the first transistor Q21 of NPN type and the second transistor Q21 of PNP type are driven complementary to each other.
22 are connected in series, and a resistor R2 is connected between the collector terminal of the second transistor Q22 and the negative conductor (-V, , ).
゜ and each of the first and second transistors Q S
A fourth transistor of NPN type Q 1 for the 21 22 series circuit of Q and resistor R22
A series circuit of a diode Q, 5NPN type fifth transformer 324, and a resistor R21 are connected in parallel, and a NPN type third transistor Q26, which is driven with a drive threshold voltage higher than the voltage drop value of the resistor R2, is connected in parallel to the transistor Q26. Second
The base terminal of the third transistor Q26 is connected to the collector terminal of the second transistor Q22, and the first and second transistors Q and Q2 are connected in parallel to the transistor Q and the resistor R22.
Configuration 21 22 where the connection point of is the output terminal T
It is out.

Next, the operation of the circuit of this embodiment based on the above configuration will be explained. First, each collector output is output from the transistors Qoi'Qo2 connected in parallel in the current switch section (C8 section) 1, and the emitter follower section (EF section) 2 operates as an OR circuit based on one of the collector outputs.
Emitter follower section (EF
Section) 3 operates as a NOR circuit.

Emitter follower section (when the collector output from the current switch section (C8 section) 1 is an H level signal
The operation of EF section) 2 is as follows. The above H level signal causes each of the first and fourth transistors Q SQ
Since both transistors 123 and ct are in the ON state and the second transistor Q22 is in the OFF state, current is supplied to the load side through the output terminal T.

When the collector output from the current switch section (C8 section) 1 is input with a signal of L level (for example, -0.5V), each of the first and fourth transistors Q and Q
123 are both in the OFF state, and the second transistor Q22 is in the ON state.

In this state, the current supplied to the load side is discharged through the second transistor Q22 which is in the ON state, and this discharged charge is detected as a voltage drop by the resistor R22.

If the current due to the voltage drop of this resistor R22 is ΔI, then
ΔI is superimposed on the steady current l and flows from the collector terminal of the second transistor Q22, and a voltage corresponding to this superimposed current (I+ΔI) is applied to the base terminal of the third transistor Q26, turning it into an ON state. Become.

The third transistor Q26, which is in the ON state, shunts the load-side discharge current from the output terminal T, and promotes discharge of the transistor Q26 along with the series circuit 2 of the second transistor Q and the resistor R22. .

The third transistor Q26 is almost OF during normal operation.
It is in the F state and is driven by the load charge itself due to discharge only when the output signal falls, so that the steady power consumption of the emitter follower section (EF section) 2 that operates complementary to it does not increase.

Furthermore, the operation of the circuit of this embodiment will be explained in detail based on specific numerical values. 1st, 21st and 4th tigers 21 22
23. Flow transistor Q SQ to diode Q24
, Q are each 0.1 (mA), and the resistor R22 is assumed to be 6 (kΩ).Here, for convenience, it is assumed that the first transistor Q and the fourth transistor Q 1 21
Since it is assumed that the transistor Q of 23.2 and the diode Q24 each have the same emitter area of about 2,
1 and C23, and C22 and C24 are now equal, but they do not necessarily have to be configured equally.

In the state of the above assumed numerical values, the resistance R in the steady state
The potential difference between both ends of Q22 is 0.6 (V), and the current flowing through the third transistor Q26 is almost negligible. Here, assuming an output fall state (applying a voltage of L level (for example, -0.5V) to human power), the base potentials of the first transistor Q21 and the fourth transistor Q23 fall. At this time, the fourth transistor Q
Since the wiring load capacitance of transistor 23 is smaller than that of the first transistor Q21, the potential drop at the emitter portion occurs faster than that of the first transistor Q21. This potential drop causes the anode of the diode Q24, that is, the second transistor Q
The base potential of Q22 also falls relatively quickly, and the second transistor Q22 is turned on. By driving the second transistor Q22, the current flowing through the resistor R22 increases, and a voltage exceeding the driving threshold voltage of the third transistor Q26 is applied.
is set to ON state.

The third transistor Q26 in this ON state accelerates the discharge of the load-side discharge current from the output terminal T2. When the discharge of this output terminal ends and the potential becomes a low level, the base-emitter voltage V of the second transistor Q22 becomes small (becomes), and the current flowing through the resistor R22 becomes steady, and the fourth transistor Q26
is set to OFF state.

Further, in the above embodiment, the first and third transistors Q 1 and Q are configured as NPN type transistors, and the second transistor 126 and transistor Q22 are configured as PNP type transistors, but the first and third transistors Q SQ126 It is also possible to configure the second transistor Q22 as each transistor of the PNP type.

Furthermore, in the above embodiment, a configuration is added to the conventional circuit as a set including a resistor R2° for detecting discharge and a third transistor Q26 which turns on and promotes discharge when discharge is detected by the resistor. However, it is not limited to one set, and a configuration in which a plurality of arbitrary sets can be connected as shown in FIG. 3 can be adopted.

Furthermore, in the above embodiment, the resistor R for detecting discharge
22, however, it can also be configured with an impedance element other than a resistor.

〔Effect of the invention〕

As described above, according to the present invention, an impedance element is connected to a pair of transistors that are connected so as to be driven in a complementary manner, and the transistors are driven at a driving threshold voltage higher than the voltage drop value of the impedance element during steady state. By adopting a parallel connection configuration, the discharge current is detected by an impedance element, the transistor is turned on, and discharge can be performed in a short time through a discharge path that passes through multiple transistors, improving drive capability by speeding up current switching. Make the most of your efforts. It also has the effect of simplifying the circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is a circuit configuration diagram according to one embodiment of the present invention, FIG. 3 is a circuit diagram according to another embodiment of the present invention, and FIG. 4 is a conventional circuit configuration diagram. A circuit configuration diagram of a power supply switching type logic circuit is shown. 1... Current switch section (C8 section) 2.3... Emitter follower section CEF section) 4... Positive power supply (G N
D) 5... Negative power supply (-■, ρ Q -Q , Q -Q , Q , Q , Q
~01 03 21 23 25 26
IIQQQ...Transistor 13ゝ 15ゝ 16 Q,,Q...Diode 424 RR, R, RR, R...Resistor 01 03 II 12' 21 22
ND Invention I) Hara Hani Akira v31 ■ ND

Claims (1)

[Claims] A first transistor (Q_2_1) and a second transistor (Q_2_2) are connected in series so as to be driven complementary to a high-potential power source and a low-potential power source, and the connection point is connected to an output terminal. (T_o_u_t) in the output circuit of the current switching type logic circuit, one side of the above power supply and the second transistor (Q
An impedance element (Z) is connected in series between the impedance element (Z) and the transistor is of the same conductivity type as the first transistor (Q_2_1) and is driven at a driving threshold voltage higher than the voltage drop value in steady state due to the impedance element (Z). The third transistor (Q_2_6) is connected to the second transistor (Q_2_6).
Q_2_2) and an impedance element (Z), and the third transistor (Q
_2_6) is connected to the control terminal of the second transistor (Q_
2_2) and an impedance element (Z).