JPH0317246B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a flip-flop circuit used in a place where noise is likely to occur.

(Prior Art) Conventionally, a flip-flop circuit has a circuit configuration as shown in FIG. 1, in which load resistors 12 and 13 and four transistors 6 to 9 are connected between a ground line 1 and a power supply line 2. There is. Transistor 6 is connected in parallel with transistor 7, and has its base connected to set signal input terminal 3. The base of transistor 7 is connected to output terminal 5 via resistor 11. Output terminal and ground line 1
Transistors 8 and 9 are connected in parallel between them, and the base of transistor 8 is connected to the collectors of transistors 6 and 7 via a resistor 10. A reset signal input terminal 4 is connected to the base of the transistor 9. Here, the base voltage of each transistor is as shown in FIG. If the potential difference between power line 2 and ground line 1 is stable, there will be no problem with the operation of this flip-flop circuit, but in cases such as automotive electrical components, the potential of power line 2 may become grounded due to noise from ignition sparks, etc. The voltage drops to near the potential of line 1, and transistors 6 to 9
may be cut off. in this case,
Even if power supply line 2 returns to its original level, if the set signal or reset signal does not enter the base of transistor 6 or the base of transistor 9, which of transistors 7 or 8 becomes conductive first? Since this is not known, the output 5 of the flip-flop circuit is not uniquely determined, resulting in malfunction.

(Object of the Invention) An object of the present invention is to provide a flip-flop circuit with excellent noise resistance for use in IC circuits and the like used in places where noise is likely to occur.

(Configuration, operation, and effects of the present invention) According to the present invention, the first and second transistors have collectors connected to respective loads, and the base of the first transistor is connected to the collector of the second transistor. a first resistor, a second resistor connecting the base of the second transistor to the collector of the first transistor, a first capacitive element connected in parallel to the first resistor, and a second resistor connecting the base of the second transistor to the collector of the first transistor; a second capacitive element connected between the collector and a reference potential, a third transistor whose base receives the collector output of the second transistor and whose emitter is connected to a power supply terminal via a current source, and a first transistor. A fourth transistor receives the collector output from the base and whose emitter is connected to the power supply terminal via the above-mentioned current source to form a differential amplifier together with the third transistor, and a second capacitive element is connected between the collector and emitter. A flip-flop circuit is obtained which includes a fifth transistor connected in parallel and whose base receives the collector output of the fourth transistor.

In the flip-flop circuit of the present invention, the first capacitive element, in the set state, can be used even if the power supply drops to ground potential and each transistor is cut off.
When power is restored, it acts as a speed-up capacitor and makes the first transistor conductive. or,
The second capacitive element acts to make the second transistor conductive because the capacitor is charged with electric charge even if the power supply fluctuates in the reset state and each transistor is cut off. In this way, the two capacitive elements can prevent the flip-flop circuit from malfunctioning due to instability of the power supply line.

(Embodiments of the Invention) Next, the present invention will be described in more detail with reference to the drawings.

FIG. 3 is a circuit diagram according to an embodiment of the present invention. A normal flip-flop consisting of transistors 6 to 9, etc., a differential amplifier consisting of capacitors 14 and 24, and transistors 16 to 19, etc.,
Resistors 20, 21 and transistor 2 which are the loads
2 and 23 are added. In normal operation, when a set signal is input to the set signal input terminal 3, the transistor 6 becomes conductive and the transistor 8 is cut off. Therefore, if the reset signal is not input to the reset signal input terminal 4, the collectors of the transistors 8 and 9 will be at a high potential, making the transistor 7 conductive, and even if the set signal disappears and the transistor 6 is cut off. , transistor 7 remains conductive, and its collector voltage is
remains low, and transistor 8 remains cut off. Therefore, the output terminal 5 is maintained at a high potential. Conversely, if a reset signal is input to reset signal input terminal 4 in this state,
Since transistor 9 becomes conductive, the collector voltage becomes a low potential and transistor 7 is cut off. Therefore, the collector voltages of transistors 6 and 7 become high potential, making transistor 8 conductive, and output terminal 5 is maintained at low potential even if the reset signal is no longer present.

In this circuit, if a situation occurs in which noise enters, power line 2 becomes unstable, and each transistor is cut off, first, if the set signal is input and the output is at a high potential, each transistor will be cut off. Transistor 16 in the state before
The transistors 17 and 19 of the comparator made up of transistors 17 and 19 are in a conductive state, and the capacitor 24 is discharged and has almost no charge accumulated therein. When the power supply voltage is restored in this state, capacitor 2
4, the speed-up capacitor 14 is charged, the collector voltages of the transistors 8 and 9 are brought to a high potential, the transistor 7 is made conductive, and the output is kept at a high potential. Conversely, when the reset signal is input, the capacitor 24 is charged to a high potential, so even if each transistor is cut off, the charged charge passes through the base resistor 10 and flows to the base of the transistor 8. The current flows, making the transistor 8 conductive and keeping the output at a low potential. Figure 4 shows two transistors in the comparator.
This is an example of a configuration consisting of

As described above, the flip-flop circuit of the present invention can prevent malfunctions even when used in a place where there is a lot of noise, such as in automobile electrical equipment. Furthermore, in order to maintain memory, it is common to attach large capacitance capacitors to both the set side and the reset side, but in the circuit of the present invention, the large capacitance capacitor can be one of the capacitors 24 and can be integrated into a monolithic IC. When configuring a circuit, one capacitor 14 can be made inside the IC, so
We were able to reduce the number of external parts and increase reliability.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional flip-flop circuit, FIG. 2 is a voltage waveform diagram of each part thereof, FIG. 3 is a circuit diagram of a flip-flop circuit according to an embodiment of the present invention, and FIG. 4 is a circuit diagram of a flip-flop circuit according to another embodiment of the present invention. FIG. 3 is a circuit diagram of a flip-flop circuit according to an embodiment. Transistor...6-9, 16-19, 22,
23, Resistance...10~13,15,20,21,
Capacitor...14, 24, Ground line...1,
Power line...2.

Claims (1)

[Claims] 1 first and second transistors whose collectors are connected to a power supply line via their respective loads; and a first transistor whose collectors are connected between the base of the first transistor and the collector of the second transistor.
a parallel circuit of a resistor and a first capacitor; a second resistor connected between the base of the second transistor and the collector of the first transistor; the collector of the first transistor and a reference; a second capacitor connected between the potential and the base connected to the second capacitor;
a third transistor whose base is connected to the collector of the first transistor and whose emitter is connected to the power supply line via a current source; and whose base is connected to the collector of the first transistor and whose emitter is connected to the emitter of the third transistor. a fourth transistor connected to the second capacitor to form a differential circuit together with the third transistor, an emitter-collector path connected in parallel to the second capacitor, and a base receiving the collector output of the fourth transistor. Fifth
A flip-flop circuit comprising a transistor.