JPS6192027A - Waveform shaping circuit - Google Patents

Abstract

PURPOSE:To ensure the multivibrator frequency division function of a waveform shaping circuit by unsaturating transistors (TRs) of a bistable multivibrator for transition during high level period of a pulse signal so as to decrease the storage time. CONSTITUTION:When a positive pulse signal is fed and a TR12 or 13 is turned on, its collector and base current is fed from an input terminal 3 through resistors 14 and 15 after being through a resistor 17. Then the voltage at a connecting point between the resistors 14 and 15 depends on the resistor 17, its value is higher than the base voltage of the TR12 (or TR13) and the collector voltage is lower than the voltage at a connecting point between the resistors 14, 15 by a voltage decided by the resistor 14. That is, the resistors 14, 15 and 17 are set properly to obtain the relation of VBE>VCE>Vsat so as to unsaturate the TR12 (or TR13) even when it is turned on, thereby decreasing the storage time, and a waveform shaping circuit sufficiently stable is obtained with a pulse signal having a large amplitude and a large duty cycle.

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 branch 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 loads. 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. and 2 are power supply terminals, terminal 2 is usually grounded, and terminals 4 and 5 are output terminals. Third and fourth transistors 12 and 13 and resistor 14
and 15 form a trigger circuit for driving transistors 10'f6 and 11, and terminal 3 is a trigger signal input application terminal. transistor 1
The emitters of transistors 0 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 II through the resistor 7 and also to the output terminal 5. The bases of transistors 10 and 11 are connected to the collectors of transistors 11 and 10 through resistors 8 and 9. The emitters of transistors 12 and 13 are connected to the bases of transistors 11 and 10, and the bases of transistors 12 and 13 are connected to the collectors of transistors 13 and 12.
The collectors of resistors 2 and 13 are connected to input terminal 31 through resistors 14 and 15. 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 values.

The operation of such a waveform shaping circuit is as follows.

When the first transistor 10 is on, a voltage is applied to the base of the second transistor 11 through the resistor 8, which is the saturation α voltage of the transistor 10. Since the forward avoidance pressure 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, and the transistor 10 is in a stable state. Now input terminal 31
If this positive trigger signal is applied, the transistor 12
Comparing the emitter potential of transistor 1 and 13,
Since the emitter potential of transistor 3 is higher, the transistor 12 is turned on, and a current flows to the collector and is determined by the resistor 1'S, and a current flows to the base, which is determined by the resistor 1'S.The sum of the currents passes through the emitter and flows to the base of the transistor 11. Because of this current, transistor 11 is forced to turn 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. So in the end it works like this.

The state is stabilized with transistor 10 off and transistor 11 on. At this time, transistor 13 is in an off state.

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

The trigger signal 20 shown in FIG. 2 has a repetition frequency of 1/T, which is a value sufficiently smaller than the resolution frequency fm at which the operation of the bistable multivibrator becomes unstable at frequencies higher than that, and the time of the positive pi level period. TL! , the time of the low level period near the ground potential is defined as tL, and the width of the signal can be changed manually.

The signal state of the output terminal 4 is represented as an output signal 24,
The amplitude is B and the repetition frequency is 1/2T. In other words, assume that the transistor 10 is on and the transistor 11 is off in a stable state during the period when the pulse signal 20 is at a low level.
At the moment when the pulse signal increases to high level, transistor 1
2 turns on, the transistor 11 turns on and the transistor 10 turns off, transitioning to a stable state, and the pulse signal 2
During the high level of 0, the transistor 12 is on, and the moment the level decreases to low, the transistor 12 is turned 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 a transistor 10 (or 11) is alternated every period T, and a frequency is repeatedly output. After the long transistor 12 (or 13) is in the on state for a certain period (to,), it is in the cutoff state for the next period (tL, +tH2+tJ).

In such a waveform shaping circuit, when a pulse signal 20 with a short low level period tL, that is, a large chicity cycle tH/T is applied, the transistor 12 (or 13) which is on during the high level period tH changes the pulse signal to a low level. Even if 20 decreases, transistor 12 (or 13) remains on, and the transistor 12 (or 13) remains on even at the next high level pulse signal, and the bistable multivibrator does not transition to 0. This is a high level period tH! 2! A certain transistor 12 (or 13) in a 0-state IC is in a saturated state for the accumulation time during the low level period when there is no drive signal, and then turns off, but in contrast to this accumulation time l, the low level period tL is For short pulse signals, transistor 12 (or 13) is always in a saturated state, and only transistor 11 (or 10) 1 on one side of transistors 10 and 11 that constitute the bistable multivibrator is driven, and the bistable multivibrator is One stable state will be maintained.

The storage time of a transistor is determined by the structural conditions of the element, characteristics (eg, epitaxial layer thickness, etc.) (eg, common emitter forward current amplification factor hFE, etc.), circuit conditions, etc. In Figure 3, the horizontal axis shows the low level period tL of the pulse signal.
FIG. 3 is a diagram showing the stable operating region of a bistable multivibrator when the amplitude of the pulse signal is plotted on the vertical axis, and region A is the stable operating region of the conventional waveform shaping circuit. Third
As shown by region A in the figure, even in the same stable operating region,
When the low level period tL of the pulse signal is small, the amplitude range of the pulse signal becomes narrow. This is because at amplitudes smaller than region A, there is insufficient drive current to reverse the stable state of the bistable multivibrator.
Furthermore, when the amplitude is larger, the accumulation time of the transistor 12 (or 13) described above is longer than the low level period t of the pulse signal.
Since it is larger than L, transistor 12 (or 13
) indicates that the bistable multivibrator does not reverse when it is in a saturated state.

As described above, the conventional waveform shaping circuit including a bistable multivibrator and a tri-power circuit has the disadvantage that when the pulse signal's chicty cycle becomes dog, the transition of the bistable multivibrator is not performed and the branching function is lost. Was. Furthermore, even if the duty cycle of the pulse signal becomes slightly small, the bistable multi-pie break does not similarly transfer to fluctuations in the amplitude of the pulse signal, making it extremely 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 it has a branching function. The object of the present invention is to obtain a waveform shaping circuit that allows easy 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 an emitter whose emitter is connected to the third transistor. The base of the second transistor is connected to the collector of the fourth transistor, whose emitter is connected to the base of the first transistor, and whose base is connected to the collector of the fourth transistor. The base is connected to the collector, one ends of the first and second resistors are connected to the collectors of the third and fourth transistors, respectively, and the other ends of the first and second resistors are connected to a common connection point. A waveform shaping circuit is obtained, characterized in that a third resistor is connected between the trigger input terminal and the trigger input terminal.

In the conventional waveform shaping circuit described above, the third or fourth transistor (12, 13) of the trigger circuit remains saturated, so the bistable multivib break does not transition and the branching function is lost. Transistor (
12, 13) Since the accumulation time at the time of saturation is longer than the low level period tL of the pulse signal, the second or third resistor causes the third or third resistor to Four transistors (12゜1
This problem can be solved by reducing the accumulation time so that 3) does not become saturated.

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

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 the first and second waveform shaping circuits. The connection point between the resistors 14 and 15 is connected to the input terminal 3 through the fourth resistor 17. In the first embodiment shown in FIG. 5, the operation of the trigger circuit is such that when the transistor 12 is turned on when a positive pulse signal is applied, its collector current and base current are passed through the resistor 17 from the input terminal 3. It will be supplied through the resistors 14 and 15, and when the transistor 13 is turned on, its collector current and base current will be supplied from the input terminal 3 through the resistor 17 and then through the resistors 15 and 14. Therefore, resistors 14 and 15 when applying a positive pulse signal
The voltage at the connection point is determined by the resistor 17, and its value is lower than the base voltage of the transistor 12 (or 13).Furthermore, the collector voltage of the transistor 12 (or 13) is determined by the voltage determined by the resistor 14 and the voltage of the resistors 14 and 15. The voltage will be lower than the voltage at the connection point. That is, VBE□(1s)>VCEI t
<Is)>Vsatuθ)) Resistance 14.
By appropriately setting transistors 15 and 17, transistor 12 (or 13) will not saturate even if it is turned on.
The accumulation time can be extremely reduced, and a waveform shaping circuit can be obtained that is sufficiently stable even for a large amplitude pulse signal with a duty cycle.

In the above description, the first, second, third, and fourth transistors are described as NPNfiPNP type transistors, but the present invention is effective and similar effects can be obtained even when PNP type transistors are used as these transistors. Needless to say.

As described above, the present invention has a very simple configuration and can perform stable circuit operation even in the case of a pulse signal with a large duty cycle without impairing the function of a conventional waveform shaping circuit.

Furthermore, since the waveform shaping circuit according to the present invention can obtain stable operation even when a pulse signal with a large S width is used, the waveform shaping circuit is stable even with fluctuations in amplitude caused by power supply voltage, ambient temperature, variations in elements, etc. Setting of elements constituting the shaping circuit also becomes easier.

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 with an integrated circuit is at most several 109 F, and this capacitor can be constructed from only transistors and resistors without metal caps, and transistors or resistors placed adjacent to each other on the same semiconductor integrated circuit board. This is because a product with uniform characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional waveform shaping circuit, FIG. 2 is a diagram of the width of the trigger pulse signal and the output signal with respect to time, and FIG. 4 is a graph showing a stable operation region in terms of the amplitude of a pulse signal with respect to the low level period of the pulse signal, and 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,
15.17・River...Resistance, 10,11,12.13...
...transistor. χ・l Figure Cha 2 Figure 3rd eye 2ρ Hee 27←

Claims (1)

[Claims] a bistable multivibrator having first and second transistors, the base and collector of the first transistor being coupled to the collector and base of the second transistor; and third and fourth transistors;
having first and second resistors and a trigger input terminal;
a trigger circuit that triggers the bistable multivibrator in response to a trigger signal supplied to the trigger input terminal, the base and collector of the third transistor being coupled to the collector and base of the fourth transistor, respectively. The collector-emitter conductive path of the third transistor is provided between one end of the first resistor and the base of the first transistor, and the collector-emitter conductive path of the fourth transistor is provided between the first end of the first resistor and the base of the first transistor. In a waveform shaping circuit that is provided between one end of the resistor and the second transistor and the base, and the other ends of the first and second resistors are connected in common, A waveform shaping circuit characterized in that a third resistor for preventing saturation of the third and fourth transistors is connected between a common connection point at the end and the trigger input terminal.