JPS5816808B2 - optical oscillation circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to an optical oscillation circuit.

FIG. 1 shows a conventional optical oscillation circuit using an optical oscillation device 1 constructed from a four-layer PnPn semiconductor device similar to the photosensitive solid-state oscillation device disclosed in Japanese Patent Publication No. 51-36991. It is something.

The light oscillation device 1 includes a p-type semiconductor impurity layer 1b formed on one side of an n-type semiconductor impurity substrate 1a, an n-type semiconductor impurity layer 1d formed on a portion of the other side, and an n-type semiconductor impurity layer 1d formed on the p-type semiconductor impurity layer 1c. The semiconductor impurity layer 1d is expanded and formed, and a collector C electrode is provided on the n-type semiconductor impurity substrate 1a, an emitter E electrode is provided on the n-type semiconductor impurity layer 1d, and a base B electrode is provided on the n-type semiconductor impurity layer 1d. It was formed.

By the way, as shown in FIG. 1, a DC power source 2 is connected between the collector C and the emitter E through an output load resistor 3 in a direction opposite to the junction between the n-type semiconductor impurity layer 1d and the n-type semiconductor impurity substrate 1a. Connect it so that the power supply voltage is applied,
When the side including the collector C is irradiated with the light X as shown in the figure, oscillation is started due to the change in the internal constant of the element due to the irradiation of the light X.

That is, when the light X is irradiated, a photovoltaic force is generated at the PN junction between the n-type semiconductor impurity substrate 1a and the p-type semiconductor impurity layer 1'b, and the junction is forward-biased and forms a four-layer npnp cyrisk structure. The state is the same as when the gate current flows in , and the current starts to flow in the path shown in the figure (■), and the junction between the n-type semiconductor impurity layer 1d and the n-type semiconductor impurity layer 1d becomes conductive, and as a result, the path shown in the figure ◎ occurs. Current also flows through the

However, when the SIRISK structure is turned on, the potential of the p-type semiconductor impurity layer 1b becomes close to the potential of the n-type semiconductor impurity layer 1d, and the left side in the figure of the junction between the n-type semiconductor impurity substrate 1a and the p-type semiconductor impurity layer 1b. The portion is reverse biased with the impurity substrate 1a serving as a positive electrode and the impurity layer 1b serving as a negative electrode.

At this time, the current flowing through the junction between the impurity substrate 1a and the impurity layer 1b is a photocurrent caused by irradiation with the light X and a charging current that charges the junction capacitance existing at the junction.

This charging current decreases as charge is accumulated in the junction capacitance, and eventually reaches zero.

At this time, the current flowing through the path (2) is only a photocurrent, and if this photocurrent is less than the holding current of the npnp thyristor structure, the thyristor becomes non-conductive.

In other words, the junction between the p-type semiconductor impurity layer 1c and the n-type semiconductor impurity substrate 1a becomes non-conductive, and the current in the @ path is also cut off.Even if the current is cut off, the potential of the n-type semiconductor impurity layer 1b is n. For a while, n
The potential is lower than that of the type semiconductor impurity substrate 1a.

(The resistance of the n-type semiconductor impurity substrate 1a is higher than that of the impurity layer 1b, and a relatively large potential difference is generated between the left and right sides of the n-type semiconductor impurity substrate 1a due to the current flowing through the path marked with ◎.

Charge is accumulated in the junction capacitance by the amount of this potential difference [If the light Forward biased.

This process is repeated to maintain oscillation.

Therefore, the photocurrent changes depending on the intensity of the irradiation light X, and the discharge time of the charge in the junction capacitance between the n-type semiconductor impurity substrate 1a and the n-type semiconductor impurity layer 1b changes.

As a result, the oscillation frequency of the optical oscillation element 1 changes depending on the amount of irradiated light X.

On the other hand, when the amount of incident light is strong, the photocurrent flowing through the junction increases, and even if the charging current of the junction capacitance becomes zero, the current exceeds the holding current of the Cyrisk structure and the photo-oscillation element 1 continues to be conductive.

Figure 2a shows the circuit current I in the absence of light X, Figure 2 shows the circuit current I in the case of weak light X irradiation, and Figure 2C shows the circuit current I in the case of moderate light X irradiation. I and the circuit current ■ when the above-mentioned conduction is maintained.

becomes constant as shown in Figure 2 d, and oscillation stops. An object of the present invention is to provide an optical oscillation circuit that does not stop and can change the oscillation frequency according to the intensity of light in the same way as when the intensity of light is low.

FIG. 3 shows a circuit diagram of one embodiment, which will be explained below with reference to the embodiment.

The embodiment circuit shown in FIG. 3 is the conventional circuit shown in FIG.

Therefore, when the light irradiated to the optical oscillation element 1 is relatively weak, the optical oscillation element 1 oscillates in the same manner as the conventional circuit.

Next, the operation when strong light X is incident as shown in FIG. 2d will be explained.

If light X corresponding to 2'd in Figure 2 is incident, the voltage drop across resistor 3 is V.

is V. -Io, B.

(However, io is the circuit current R is the resistance value of the resistor 3 which is the load resistance.) However, the Zener voltage Vz of the Zener diode 4 is a voltage drop ■.

When it is smaller, i.e. V.

> Vz, a reverse voltage is applied between the emitter E and the base 8 of the optical oscillation element 1, cutting off the current flowing through the optical oscillation element 1, and turning off the optical oscillation element 1.

Once this light oscillation element 1 transitions from the on state to the off state, the junction between the collector C and the gate G, which had been forward biased until then, has a junction capacitance.
, gate G) is also reverse biased.

The reverse bias between the emitter E and the base 8 disappears at the same time that no current flows through the optical oscillator 1 and the optical oscillator 1 turns off, and this junction (emitter E, base 8
(between), as long as light is incident, the light oscillation element 1
becomes forward biased as soon as it turns off.

However, the junction between the collector C1 and the gate G remains reverse biased for a while after the photo-oscillator 1 turns off due to the junction capacitance, and until this reverse bias is removed by the photocurrent, the photo-oscillator The off state of 1 continues.

Therefore, when the light intensity is increased, the photocurrent flowing between the collector C and the gate 0 becomes larger.

The time during which data 1-0 is biased in the reverse direction becomes shorter, and as the incident light increases, the oscillation frequency also becomes higher as shown in FIG.

Although it is preferable to take the output from both ends of the resistor 3, it is also possible to insert another resistor between the collector C and the power supply 2 and take the output from both ends.

As described above, the present invention connects the Zener diode between the negative electrode side of the power supply and the base of the optical oscillation element, thereby achieving
It is possible to sustain oscillation even when the incident light is strong, and has the effect of greatly expanding the intensity range of light in which the oscillation frequency changes.

[Brief explanation of the drawings] Fig. 1 is a conventional circuit diagram, Fig. 2 a to d are explanatory diagrams of the same operation as above, Fig. 3 is a circuit diagram of an embodiment of the present invention, and Fig. 4 is an operation same as above. 1 is an explanatory diagram, 1 is a light oscillation element, 1a is an n-type semiconductor impurity substrate, 1b and Ic are n-type semiconductor impurity layers, 1d
is an n-type semiconductor impurity layer, 2 is a power supply, 3 is a resistor, 4 is a Zener diode, B is a base, C is a collector, and E is an emitter.

Claims (1)

[Claims] 1 A semiconductor impurity layer of a conductivity type opposite to that of the substrate is formed on one side of the semiconductor impurity substrate, and a semiconductor impurity layer of the opposite conductivity type is formed on a part of the other side, and a semiconductor of the same conductivity as the semiconductor impurity substrate is formed on the upper surface of the impurity layer. At the same time as forming an impurity layer, collector, emitter, and base electrodes are formed on the surfaces of the semiconductor impurity substrate and the semiconductor impurity layer, and on the surface of the opposite conductivity type semiconductor impurity layer, respectively, and a DC power supply voltage is applied between the collector and the emitter. In an optical oscillation circuit using an optical oscillation element that oscillates by irradiating light onto the collector side of the optical oscillation element, there is a An optical oscillation circuit characterized in that a load resistor is connected and a Zener diode is connected between the negative electrode of a DC power supply and the base of an optical oscillation element.