JPS582486B2 - timer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a timer that generates signals of short time intervals.

In recent years, various types of timers have been used in data processing devices.

The simplest type of timer has a capacitor connected to the emitter of a transistor, and the transistor is turned on and off by charging and discharging the capacitor.
FF is turned on, and changes in the output on the collector side are extracted as a time signal.

However, in a timer with such a configuration,
If an attempt is made to obtain a short time signal compared to the switching characteristics of the transistor used, there is a drawback that a stable time signal cannot be obtained.

The present invention aims to provide a new timer that eliminates the above drawbacks, and an object of the present invention is to connect the emitter of a transistor to a power supply via a resistor, connect a capacitor to the emitter, and charge the capacitor. In a timer in which a signal obtained from the collector side of the transistor is used as a time signal by utilizing the fact that the transistor turns on and off due to discharge, a Schottky is connected between the emitter of the transistor and the capacitor in series with the emitter. This can be achieved by providing a barrier diode.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a circuit example diagram of a conventional timer, and FIG. 2 is a diagram of circuit operation waveforms of FIG. 1.

In FIG. 1, IN is an input signal terminal, T1 and T2 are transistors, C is a capacitor, and R is a resistor.

The resistor R is connected to the voltage source -V and constitutes a current source.

In FIG. 2, IN is the potential waveform of the input signal terminal IN,
E2 is the potential waveform at point E2 in Fig. 1, and OUT is the 1st potential waveform.
A potential waveform at a point indicating OUT in the figure is shown.

Next, the operation of the circuit shown in FIG. 1 will be explained using FIG. 2.

1}, a rectangular wave as shown in FIG. 2 IN is applied to the IN point in FIG.

Then T1 turns on, and the current flows from +V to - through T1.
Flows to V.

Since T1 is turned on and current flows, the potential on the emitter side of T1 rises to a certain level.

As a result, the potential at point E2 in Figure 1 rises instantaneously, and this E
Since the potentials at the two points become higher than the VBE of the transistor T2, the transistor T2 is turned off.

Therefore, the potential at the OUT point in FIG. 1 increases.

Capacitor C is then discharged through resistor R, and as a result, the potential at point E2 drops, and transistor T2 is turned on when the potential at point E2 drops to a potential that forward biases the pace emitter of transistor T2.

E2 in FIG. 2 shows this situation.

Therefore, the potential at the OUT point changes as shown by the solid line OUT in FIG. 2 depending on whether the transistor T2 is turned on or off.

This signal OUT in FIG. 2 is used as a time signal.

However, in reality, the waveform at point E2 in FIG. 1 becomes the waveform shown by the dotted line at E2 in FIG. 2, which is inconvenient when trying to obtain a short time signal.

That is, since the emitter capacitance of the transistor T2 is connected in series with C, the emitter capacitor is connected as an emitter load of the transistor T1, for example, like a slow speed transistor.

This is because a capacitive load is connected to the load of the emitter follower, which tends to induce parasitic vibrations of the emitter follower, causing the voltage waveform on the emitter side of the transistor to oscillate.As a result, the voltage waveform of the capacitor C It also vibrates as shown by the dotted line E20 in Figure 2.

As a result, the time signal obtained from the point OUT in FIG. 1 is subject to change due to slight fluctuations in power supply voltage or temperature changes, which is a practical problem.

FIG. 3 is a circuit diagram of a first embodiment of the present invention.

In the figure, IN is an input signal terminal, T1 and T2 are transistors, C is a capacitor, and SD is a Schottky barrier diode.

As shown in FIG. 3, the present invention is characterized in that a Schottky barrier diode is inserted in series with the emitter of the transistor (T2 in FIG. 3).

By connecting the Schottky barrier diode,
By reducing the reverse voltage capacity of the Schottky barrier diode, the capacitive load on the transistor T1 is reduced and vibration is prevented. Since the vibration is cut off by the vibration, the switching of the transistor T2 becomes constant regardless of the vibration, and its characteristics are further improved.

FIG. 4 shows a second embodiment of the present invention, in which the present invention is used in an oscillator.

In the figure, T3 and T4 are transistors and SD
I and SD2 are Schottky barrier diodes, C is a capacitor, and R1, R2, and R are resistors.

Further, FIG. 5 shows voltage waveforms at points B2, E3, and E4 in FIG. 4.

The operation of the same path shown in FIG. 4 will be explained below using FIG. 5.

In FIG. 4, it is assumed that transistor T3 is on and transistor T4 is off.

Since transistor T3 is on, capacitor C is
Emitter of transistor T3 → capacitor C → resistor R2
It is charged through the route of

At this time, the potential E4 of the emitter of the transistor T4 falls asymptotically.

E4 in FIG. 5 shows this situation.

Therefore, E4 is the emitter potential (VB
When the voltage drops to E), transistor T4 is turned on.

When the transistor T4 is turned on, the potential at the point E4 rises, so that the potential at the emitter of the transistor T3 rises all at once.

As a result, the transistor T3 turns off when the potential at the E3 point becomes higher than the VBE of the transistor T3 (
Figure 5 E3).

As shown in FIG. 5, the potentials of E4 and B2 remain constant until E3 drops and matches the emitter potential of transistor T3.

Now, when the potential of E3 matches the emitter potential of transistor T3, transistor T3 is turned on again, and E4 rises, so transistor T4 is turned off.

In other words, it returns to its initial state. In this case as well, the Schottky barrier diodes SD1 and SD2 are connected to the transistor T
3. By inserting in series to the emitter of T4, each 1
This stabilizes the switching operation of one transistor.

Therefore, the output signal of the oscillator to which the present invention is applied is a very good signal pulse that ideally rises and falls.

As described above, according to the present invention, a timer that is not affected by fluctuations in power supply voltage or temperature is possible.

Furthermore, it goes without saying that the present invention can be used not only for timers but also for transistor circuits in general.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional timer, FIG. 2 is an operation waveform diagram of the timer in FIG. 1, FIG. 3 is a circuit diagram of a timer according to the first embodiment of the present invention, and FIG. Figure 3 shows a circuit diagram of a second embodiment of the invention. In the figure, T1 and T2 are transistors, C is a capacitor,
E, E1, E2 are Schottky barrier diodes, Rl
, R2 and R indicate resistance.

Claims (1)

[Claims] 1 Connect the emitter of a transistor to a power source via a resistor, connect a capacitor to the emitter, and use the fact that the transistor turns on and off as the capacitor charges and discharges to generate a signal from the collector side of the transistor. 1. A timer in which a Schottky barrier diode is provided between the emitter of the transistor and the capacitor in series with the emitter to obtain a stable time signal.