JPH09107120A - Optical-to-electrical transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform high-speed switching response by amplifying the on/off threshold current of a light receiving element at a front step and rear step mirror circuits and outputting the amplified on/off signal from a constant current circuit. SOLUTION: An idling constant current circuit 60 outputs constant current Io of several μA, which is about the same as the threshold current Iref of a light receiving diode PD. An idling current circuit 40 is composed of transistors TrQ41 Q43 . The idling current I41 , which is to be subtracted from the collector of the TrQ41 by the TrQ42 , is about the same as the threshold current, since the idling current I41 is the same as the idling constant current Io , and the idling current I42 , which is to be subtracted from the collector of the TrQ12 by the TrQ43 , is the value obtained by amplifying the idling constant current Io at the front step mirror circuit 10. At the rear-step mirror 20, the value obtained by amplifying the current I41 at the front-step mirror circuit 10 and the current I42 are offset, and the influence of the idling circuit 40 is eliminated on the output current of the constant current circuit 30. Thus, high-speed switching is allowed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device in which a fat diode and a signal processing circuit are integrated, and more particularly to an improvement for detecting an on / off signal at a high speed and increasing a response speed of an output signal.

[0002]

2. Description of the Related Art A photoelectric conversion device is used in a semiconductor relay device or the like as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-51157 proposed by the present applicant. FIG.
FIG. 4 is a circuit diagram of a conventional device. In the figure, the pre-stage mirror circuit 10 has a pair of pnp transistors Q11 and Q12, the emitter terminal of which is connected to the power supply line Vcc,
The base terminals are commonly connected and the transistor Q
It is connected to 11 collector terminals. The collector terminal of the transistor Q11 is connected to the cathode terminal of the light receiving diode PD. The anode terminal of the light receiving diode PD is connected to the common.

The rear stage mirror circuit 20 has a pair of npn transistors Q21 and Q22. The emitter terminal is connected to common and the base terminal is commonly connected.
It is connected to the collector terminal of the transistor Q21. The collector terminal of the transistor Q21 is connected to the collector terminal of the transistor Q12. The collector terminal of the transistor Q22 is connected to the power line Vcc via the constant current circuit 30.
Is connected to The constant current circuit 30 outputs a constant current IrefxAxB obtained by multiplying the threshold current Iref related to ON / OFF of the light receiving diode PD by the amplification factor A of the front stage mirror circuit 10 and the amplification factor B of the rear stage mirror circuit 20. Output from Vo. The amplification factor A is 7 and the amplification factor B is 3, for example.

[0004]

However, according to the conventional circuit, the signal current when the light receiving diode PD is on is 100 n.
It is A to 10 μA, and is substantially 0 nA because it is only the dark current when it is off. This detection is performed by the current mirror circuit 1
When it is performed at 0 and 20, when switching from on to off, there is a problem that the switching response becomes very slow due to the accumulation of the minority carriers injected into the base terminal of the transistor (base accumulation time).

The circuit of FIG. 3 is used as a circuit for solving the influence of the base accumulation time. In the circuit of Figure 2,
An idling circuit 40 and a minute constant current circuit 50 are attached. The idling circuit 40 has a pair of npn transistors Q41 and Q42. The emitter terminal is connected to common, the base terminal is connected in common, and the minute constant current circuit 50 is connected to the power supply line Vcc. Connected to the collector terminal of the transistor Q41. The collector terminal of the transistor Q42 is connected to the collector terminal of the transistor Q11. Micro constant current circuit 50
Supplies a minute current of 10% or less with respect to the threshold current Iref of the light receiving diode PD to improve the switching response of the current mirror circuits 10 and 20.

However, according to this improved conventional circuit, the minute current value of the minute constant current circuit 50 is, for example, 10 n.
The value becomes A, and there is a problem that a constant current circuit of about several μA used in a normal circuit design cannot be adopted and a special circuit design is required. Further, even with the switching speed improved by the idling circuit, the response is slow in response to the current request for high-speed switching operation, and further higher switching speed has been required. The present invention solves such a problem, and an object thereof is to provide a photoelectric conversion device having a simple circuit design and a high switching response.

[0007]

According to the present invention for achieving the above object, there is provided a first transistor Q11 connected to a light receiving element PD and a first transistor Q11 for amplifying a current flowing through the first transistor at a predetermined ratio A. The front-stage mirror circuit 10 having the second transistor Q12, the third transistor Q21 connected to the second transistor, and the fourth transistor Q22 for amplifying the current flowing through the third transistor at a predetermined ratio B are provided. The rear-stage mirror circuit 20 having the same, the constant-current circuit 30 for outputting a constant current obtained by amplifying the threshold current Iref of the light-receiving element with an amplification factor AxB defined by the front-stage and rear-stage mirror circuits, and the threshold current of the light-receiving element The idling constant current circuit 60 that outputs a constant current Io of the same degree, the fifth transistor Q41 connected to the idling constant current circuit, and the fifth transistor Q41. A sixth transistor Q42 supplying the same current as the current flowing through the transistor to the connection point between the first transistor and the light receiving element, and the current flowing through the fifth transistor are amplified with the same amplification factor as that of the preceding stage mirror circuit, And an idling circuit 40 having a seventh transistor Q43 supplied to the connection point of the second transistor and the third transistor.

[0008]

According to the structure of the present invention, the front-stage and rear-stage mirror circuits 1 with respect to the ON / OFF threshold current of the light receiving element
The amplified on / off signal current is output from the constant current circuit 30 after being amplified by 0 and 20. The idling circuit 40 inputs a constant current of the same level as the threshold current from the idling constant current circuit 60, supplies the same idling current to the input side of the front stage mirror circuit, and supplies the same idle current to the rear stage mirror circuit. Supply the idling current amplified at the same ratio as. Then, in the constant current circuit 30,
The influence of the idling circuit 40 is eliminated by the differential configuration, and the pre-stage mirror circuit is hardly affected by the base accumulation time due to the idling current, and high-speed switching response becomes possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG.
FIG. 3 is a configuration perspective view of a photoelectric conversion device showing an embodiment of the present invention. In FIG. 1, the same components as those in FIGS. 1 and 2 are designated by the same reference numerals and the description thereof will be omitted. In the figure, the idling constant current circuit 60 outputs a constant current Io that is about the same as the threshold current Iref of the light receiving diode PD, and may be about several μA.

The idling circuit 40 includes a pair of npns.
Third transistor Q43 in addition to transistors Q41 and Q42
And the emitter terminals are connected to common and the base terminals are connected in common. The collector terminal of the transistor Q41 is connected to the power supply line Vcc through the idling constant current circuit 60, and the transistors Q41 and Q4 are connected.
It is connected to the base terminal of 2, Q43. Transistor Q
The collector terminal of 42 is connected to the collector terminal of the transistor Q11. The collector terminal of the transistor Q43 is connected to the collector terminal of the transistor Q21. The current amplification factor of each transistor Q41, Q42, Q43 is 1: 1:
A shall be satisfied.

Next, the operation of the thus constructed apparatus will be described. Since the idling current I41 drawn by the transistor Q42 from the collector terminal of the transistor Q11 is the same as the idling constant current Io, it is about the same as the threshold current. Further, the idling current I42 drawn by the transistor Q43 from the collector terminal of the transistor Q12 is
It is a value obtained by amplifying the idling constant current Io by the pre-stage mirror circuit 10. Here, in the rear stage mirror circuit 20,
The current obtained by amplifying the idling current I41 by the pre-stage mirror circuit 10 and the idling current I42 are offset, and the output current of the constant current circuit 30 eliminates the influence of the idling circuit 40.

The switching response speed is dominated by the front stage mirror circuit 10 having a small current value. Here, since the idling current I41 is supplied to the front stage mirror circuit 10, the switching operation can be performed with almost no influence of the base accumulation time, so that the response speed becomes faster.

Next, the difference in response time by simulation will be compared. Here, the threshold current Iref is set to 10
Calculated as 0 nA. Response time from ON to OFF T _ON
→ The _OFF speed is increased to a fraction of that of the conventional example as follows. Figure 1 (Example) T _ON → _OFF is ~ 5μS. Fig. 2 (Conventional example) T _ON → _OFF is 20 to 30 μS. Figure 3 (Conventional example) T _ON → _OFF is 15 to 20 μS.

[0014]

As described above, according to the present invention, since the idling circuit 40 is provided and the idling current of the same level as the threshold current is supplied to the input side of the front stage mirror circuit, the base accumulation is performed. This has the effect of performing high-speed switching operation that is hardly affected by time. Also,
The idling current amplified by the same ratio as the former mirror circuit is supplied to the latter mirror circuit, and the idling circuit 40 is supplied.
Since the influence of is eliminated by the differential configuration, there is no signal distortion. Further, since the idling constant current circuit 60 can cope with the configuration of a normal constant current circuit, there is an effect that the circuit design becomes simple as compared with the conventionally used minute constant current circuit.

[Brief description of the drawings]

FIG. 1 is a configuration perspective view of a photoelectric conversion device showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional device.

FIG. 3 is a circuit diagram of an improved conventional device.

[Explanation of symbols]

 10 Front-stage mirror circuit 20 Rear-stage mirror circuit 30 Constant current circuit 40 Idling circuit 60 Idling constant current circuit

Claims (1)

[Claims] 1. A first transistor (Q11) connected to a light receiving element (PD), and a second transistor (Q12) for amplifying a current flowing through the first transistor at a predetermined rate (A). The front-stage mirror circuit (10), the third transistor (Q21) connected to the second transistor (Q12), and the fourth transistor for amplifying the current flowing through the third transistor at a predetermined ratio (B). A rear stage mirror circuit (20) having a transistor (Q22), and a constant current circuit (aref) which outputs a constant current obtained by amplifying a threshold current (Iref) of the light receiving element with an amplification factor (AxB) determined by the front stage and rear stage mirror circuits. 30) and a constant current (Io) about the same as the threshold current of the light receiving element.
An idling constant current circuit (60) for outputting the current, a fifth transistor (Q41) connected to the idling constant current circuit, and the same current flowing through the fifth transistor as the first transistor and the light receiving element. The current flowing through the sixth transistor (Q42) and the fifth transistor supplied to the connection point of the second transistor is amplified with the same amplification factor as that of the previous stage mirror circuit, and is connected to the connection point of the second transistor and the third transistor. An idling circuit (40) having a supplying seventh transistor (Q43), and a photoelectric conversion device comprising: