JPS6220738B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waveform shaping circuit including a transistorized bistable multivibrator.

Conventionally, bistable multivibrators have been used in frequency dividing circuits and the like, and among these, there are many saturated types that use a fixed bias, which have a simple circuit configuration and are highly stable against changes in external load. A waveform shaping circuit includes this bistable multivibrator and a trigger circuit that drives the bistable multivibrator.

FIG. 1 shows an example of a conventional waveform shaping circuit,
In the figure, first and second transistors 10 and 11 and resistors 6, 7, 8 and 9 constitute a bistable multivibrator, terminals 1 and 2 are power supply terminals, and terminal 2 is normally grounded. Terminals 4 and 5 are output terminals. A trigger circuit is configured by third and fourth transistors 12 and 13 and resistors 14 and 15, and is for driving transistors 10 and 11.
Terminal 3 is a trigger signal input application terminal. The emitters of transistors 10 and 11 are grounded, and the collector of transistor 10 is connected to power supply terminal 1 through resistor 6 and also to output terminal 4. The collector of the transistor 11 is connected to the power supply terminal 1 through the resistor 7 and also to the output terminal 5. transistor 10
The bases of and 11 are connected through resistors 8 and 9 to the collectors of transistors 11 and 10. The emitters of transistors 12 and 13 are connected to the bases of transistors 11 and 10, the bases of transistors 12 and 13 are connected to the collectors of transistors 13 and 12, and the collectors of transistors 12 and 13 are connected to the input through resistors 14 and 15. Connected to terminal 3. In the above circuit configuration, it is preferable that transistors 10 and 11, 12 and 13 have the same characteristics, and resistors 6 and 7, 8 and 9, and 14 and 15 have substantially the same resistance value.

The operation of such a waveform shaping circuit is as follows. , when the first transistor 10 is on, the saturation voltage of the transistor 10 is applied to the base of the second transistor 11 through the resistor 8; Since the forward voltage is sufficiently large, the transistor 11 is turned off, and the current determined by the resistors 7 and 9 continues to flow through the base of the transistor 10, which is in a stable state. If we now apply a positive trigger signal to input terminal 3, when we compare the emitter potentials of transistors 12 and 13, the emitter potential of transistor 13 is higher, so transistor 12 is turned on, and the current determined by resistor 14 flows into the collector as the base. A current determined by the resistor 15 flows through each of the resistors 15 and the sum of the currents flows into the base of the transistor 11 through the emitter, so that the transistor 11 is forcibly turned on. At this time, the collector potential of the transistor 11 decreases, and this voltage is transmitted to the base of the transistor 10 and acts to reduce the collector current of the transistor 10. This current change is detected by the resistor 6 and increases the base current of the transistor 11. Eventually, the transistor 10 is off and the transistor 11 is on, resulting in a stable state. At this time, transistor 13 is in an off state.

The above operation will be explained in the case where the trigger signal shown in FIG. 2 is applied.

The trigger signal 20 shown in FIG. 2 has a repetition frequency of 1/T, and this value is sufficiently smaller than the resolution frequency m, at which the operation of the bistable multivibrator becomes unstable at frequencies above which the operation of the bistable multivibrator becomes unstable. This is a signal whose time is t _H , the time of the low level period near the ground potential is t _L , and whose amplitude is represented by A. The signal state at output terminal 4 is represented as output signal 24, with amplitude B and repetition frequency 1/2T. That is, when the pulse signal 20 is at a low level, the transistor 10 is turned on and the transistor 1 is turned on.
1 is in a stable state in which the pulse signal 20 is off, and at the moment when the pulse signal increases to high level, the transistor 12 turns on, which transitions to a stable state in which the transistor 11 is on and the transistor 10 is off, and the pulse signal 20 is in a high level period. The transistor 12 is on, and the instant the voltage decreases to low level, the transistor 12 turns off, but one stable state of the bistable multivibrator continues.

The next high-level pulse signal 20 turns on the transistor 13, and returns to the original stable state through an operation completely symmetrical to that described above. The on/off state of such transistor 10 (or 11) is alternated every period T, and a square wave output signal 24 with a repetition frequency of 1/2T is output from terminals 4 and 5. Further, after the transistor 12 (or 13) is in the on state for a certain period (t _H1 ), it is in the cut-off state for the next (t _L1 +t _H2 +t _L2 ) period.

In such a waveform shaping circuit, the low level period t
When a pulse signal 20 with a short _L , that is, a large duty cycle t _H /T is applied, the transistor 12 is turned on during the high level period t _H
(or 13) becomes low level pulse signal 20
Even if the transistor 12 (or 13) decreases,
is in the on state, and the transistor 12 (or 13) continues to be in the on state even at the time of the next high-level pulse signal, so that the bistable multivibrator does not transition. This means that the transistor 12 (or 13) is saturated during the high level period _tH .
During the low level period when there is no drive signal, transistor ₁ is in a saturated state for the accumulation time and then turns off.
Transistor 1 (or 13) is always in a saturated state and constitutes a bistable multivibrator.
Since only the transistors 11 (or 10) on one side of transistors 0 and 11 are driven, the bistable multivibrator maintains one stable state.

The storage time of a transistor is determined by the structural conditions of the element, characteristics (eg, epitaxial layer thickness, etc.) (eg, grounded emitter forward current amplification factor h _FE , etc.), circuit conditions, etc. FIG. 3 is a diagram showing the stable operating region of a bistable multivibrator when the horizontal axis is the low level period t _L of the pulse signal and the vertical axis is the amplitude of the pulse signal, and region A is the conventional waveform shaping. This is the stable operating area of the circuit. As shown by region A in FIG. 3, even in the same stable operation region, the amplitude range of the pulse signal becomes narrower where the low level period t _L of the pulse signal is small. This is because when the amplitude is smaller than that in region A, there is insufficient drive current to reverse the stable state of the bistable multivibrator, and when the amplitude is larger than that of the transistor 12 (or 13).
Since the accumulation time of t L is longer than the low level period t _L of the pulse signal, the transistor 12 (or 1
3) is in a saturated state and the bistable multivibrator does not reverse.

As described above, the conventional waveform shaping circuit that includes a bistable multivibrator and a trigger circuit has the disadvantage that when the duty cycle of the pulse signal becomes large, the transition of the bistable multivibrator is not performed and the frequency dividing function is lost. was. Furthermore, even if the duty cycle of the pulse signal becomes a little small, the bistable multivibrator will not shift in response to fluctuations in the amplitude of the pulse signal, making it very difficult to set the amplitude of the pulse signal.

In view of the above-mentioned drawbacks, the present invention increases the duty cycle of the pulse signal with a simple circuit configuration, and furthermore, the transition of the bistable multivibrator is performed even in response to fluctuations in the amplitude of the pulse signal, and the present invention has a frequency dividing function. It is also an object of the present invention to provide a waveform shaping circuit that facilitates setting of the amplitude of a pulse signal.

According to the present invention, in the waveform shaping circuit configured with a bistable multivibrator including first and second transistors and a trigger circuit including third and fourth transistors, the third transistor has its emitter The fourth transistor has its emitter connected to the base of the first transistor and its base connected to the collector of the third transistor. an input terminal connected to the base and supplying a trigger signal current to the third and fourth transistors;
means for at least a portion of the base current and collector current of each of the third and fourth transistors inserted between the input terminal and the collectors of the third and fourth transistors to serve as a common path; There is obtained a waveform shaping circuit characterized in that the collector-emitter voltage of each of the third and fourth transistors is set to be larger than the saturation voltage of each of the transistors.

Since the third or fourth transistors 12 and 13 of the trigger circuit in the conventional waveform shaping circuit described above remain saturated, the bistable multivibrator does not transition and loses its frequency dividing function. The accumulation time when signals 12 and 13 are saturated is the low level period t of the pulse signal 20.
Since the cause is that the voltage is larger than _L , the problem can be solved by reducing the accumulation time by preventing the third or fourth transistors 12 and 13 from being saturated during the high level period of the pulse signal 20.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A waveform shaping circuit according to the present invention will be described below based on embodiments with reference to the drawings.

Therefore, one embodiment of the waveform shaping circuit of the present invention is shown in FIG. 4. The same parts as the conventional waveform shaping circuit (see FIG. 1) are given the same reference numerals, and the different parts are shown in the third and fourth parts. The collectors of transistors 12 and 13 are connected through a third resistor 16. In the waveform shaping circuit with the above configuration, the operation of the bistable multivibrator is the same as that of the conventional example, and the operation of the trigger circuit is such that when a positive pulse signal is applied, if the transistor 12 is turned on, its collector current is changed to the resistor 14. A current that is the sum of the current determined by the resistor 15 and a current in which a part of the current determined by the resistor 15 flows through the resistor 16 flows.
When the transistor 13 is turned on, the direction of the current flowing through the resistor 16 is simply reversed. Normally, when the collector current flowing to the collector of a transistor is several hundred μA, the saturation voltage V _CE (sat) of the transistor is smaller than the forward voltage V _BE between the base and emitter of the transistor, so the current flowing to the resistor 16 is the same as that of the transistor 12 (or 13). The current is determined by the difference voltage between the base potential and the collector potential of the resistor 16 and the resistor 16, that is, V _R16 <V _BE12(1
3) -V _sat12(13) (However, V _R16 ; Voltage across resistor 16, V _BE12(13) ; Base-emitter forward voltage of transistor 12 or 13, V _sat12(13) ; Voltage across transistor 12 or 13. By setting the transistor 12 (or 1
3) collector potential is determined, V _CE12(13) > V _sat1
2(13) (However, V _CE12(13) ; Transistor 12 or 1
(Collector-emitter voltage of 3). In other words, the resistor 16 can be set so that it does not saturate even if the transistor 12 (or 13) is turned on, so the high level period t _H of the pulse signal is the same as that of the transistor 12 (or 13).
does not saturate, and therefore its accumulation time is extremely short, and it responds quickly to changes in the pulse signal, so it is in the off state during the low level period, and the trigger circuit and twin This means that the operation is equivalent to that of a stable multivibrator, and a bistable multivibrator makes a stable transition and has a frequency dividing function. Region B in Figure 3 shows the stable operating region of the waveform shaping circuit of the present invention, which is much wider than the conventional region A, and is suitable for pulse signals with large duty cycles and large amplitudes. It was also experimentally confirmed that the system operates stably. Further, in the above explanation, the collector potential of the transistor 12 (or 13) that is turned on is such that the common emitter forward current amplification factor h _FE of that transistor is usually larger than 1, and the resistance values of the resistors 14 and 15 are the same. If the characteristics of transistors 12 and 13 are the same, the potential is lower than their base potential, so
The transistor 13 (or 12) will not turn on and the bistable multivibrator will not operate unstablely.

In the above explanation, the first, second, third, and fourth transistors were described using NPN transistors, but the present invention is effective and the same effects can be obtained even when PNP transistors are used as these transistors. Needless to say, it can be done.

As described above, according to the present invention, it is possible to perform stable circuit operation even in the case of a pulse signal having a large duty cycle with a very simple configuration without impairing the function of a conventional waveform shaping circuit.

In addition, since the waveform shaping circuit according to the present invention can obtain stable operation even when a pulse signal has a large amplitude, it is stable even against fluctuations in amplitude caused by power supply voltage, ambient temperature, variations in elements, etc., so the waveform shaping circuit It also becomes easier to set up the elements that make up the .

Further, the waveform shaping circuit according to the present invention is effective when integrated into an integrated circuit. In other words, the capacitance of a capacitor that can be obtained in an integrated circuit is approximately several tens _{of PF} at most, and it can be constructed with only transistors and resistors that do not include this capacitor, and transistors or resistors placed adjacent to each other on the same semiconductor integrated circuit board are This is because a product with uniform characteristics can be obtained.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional waveform shaping circuit.
FIG. 2 is a diagram of the amplitude of the trigger pulse signal and the output signal with respect to time, and FIG. 3 is a diagram showing the stable operating region with the amplitude of the pulse signal with respect to time (low level period of the pulse signal) to explain the effects of the present invention. FIG. 4 is a circuit diagram showing an embodiment of the waveform shaping circuit according to the present invention. 1, 2...Power terminal, 3...Input terminal, 4,5
...Output terminal, 6, 7, 8, 9, 14, 15, 1
6...Resistor, 10, 11, 12, 13...Transistor.

Claims (1)

[Claims] 1 a bistable multivibrator having a first and a second transistor, the base and collector of the first transistor being coupled to the collector and the pace of the second transistor; and a third and fourth transistor. , a trigger circuit having first and second resistors and a trigger input terminal, the trigger circuit triggering the bistable multivibrator in response to a trigger signal applied to the trigger input terminal; A base and a collector are coupled to the collector and base of the fourth transistor, respectively, and a collector-emitter conductive path of the first resistor and the third transistor connects the trigger input terminal and the base of the first transistor. In the waveform shaping circuit, the second resistor and the collector-emitter conductive path of the fourth transistor are connected in series between the trigger input terminal and the base of the second transistor. A waveform shaping circuit characterized in that a third resistor for preventing saturation of the third and fourth transistors is connected between the collector of the third transistor and the collector of the fourth transistor.