JPS6214076A - Light receiving apparatus - Google Patents

Abstract

PURPOSE:To achieve a higher distance measuring accuracy, by providing a lower frequency attenuating capacity between a light receiving element and a current amplifying transistor while first and second current conversion means are provided to inhibit the effect of low frequency extraneous light and the effect of temperature changes. CONSTITUTION:A low frequency attenuating capacitor 34 is provided between a light receiving element 7 and the base of a current amplifying transistor 19. A first current conversion means which comprises a first current mirror circuit 36 for outputting current corresponding to the collector current of the current amplifying transistor 19 to a logarithmic compression diode element 23 and a first constant current source 37 and a second current conversion means which comprises second, third and fourth current mirror circuits 39, 42 and 46 having the value corresponding to the current flowing through a logarithmic compression diode element 24 as the emitter current of the current amplifying transistor 19 and a second constant current source 27 are provided. This can inhibit the effect of low frequency extraneous light and the effect of temperature changes.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a distance measuring device used in, for example, a camera, which measures the distance to a distance-measuring object by receiving a signal light reflected from the distance-measuring object. The present invention relates to a light receiving device, and particularly to a light receiving device having a light receiving element and an amplifier circuit.

[Conventional technology]

In general, in this shelf distance measuring device, a pair of light receiving elements arranged in close proximity receive a signal light reflected from an object to be measured, and a photovoltaic current of the light receiving element generated by this signal light is generated. By determining the ratio, the distance to the object to be measured is determined.

FIGS. 2 and 3 show this type of distance measuring device. First, as shown in FIG.
) is incident on the object to be measured (8a) or (8b) lζ, and the reflected signal light (4a) or (4b) is transmitted to a photodetector element having a pair of light-receiving confections (7a) (7b). (3
PI) is input to t61. This photodetecting element (6)
is composed of an N-type semiconductor substrate (6C) which serves as a cathode, and a P-type semiconductor layer (6a) (6b) which serves as an anode formed on one main surface of this semiconductor substrate. Now, if the signal light (4a) reflected from the object (8a) to be measured at a short distance is incident, a large amount of signal light (4a) will be reflected on the light receiving element (7a) as shown in Fig. 3. Therefore, a large photovoltaic current flows through the light receiving element (7a), and a small photovoltaic current flows through the light receiving element (7b). Long distance again! Assume that the signal light (4b) reflected from a certain object to be measured (8b) is incident. As shown in Fig. 3, the light receiving element (7b) has many signal lights (4b
) is incident on the photodetector (7b), a large photovoltaic current flows in the photodetector (7b), and a small photovoltaic current flows in the photodetector (7a).As shown in FIG. The flowing photovoltaic current is converted to a voltage value corresponding to the photovoltaic current by the photoreceptor (8a), and is inputted to one input terminal of the operational amplifier f12 via the buffer amplifier (1G and a resistor ring).

On the other hand, the photovoltaic current flowing through the light receiving element (7b) is
8b) to a voltage value corresponding to the photovoltaic current fζ, and is applied to the operational amplifier 02 via the buffer amplifier 13 and the resistor I.
is input to the other input terminal of. In addition, the operational amplifier tlZ
One input terminal and output terminal of the circuit are connected through a resistor uS, and the other input terminal is connected to a base voltage source ue through a resistor lI'rI. Operational amplifier +IZ and resistor an (141 (IS uη) constitute a differential amplifier, so the output corresponding to the difference voltage between the two input terminals of the operational amplifier 112 is the operational output @ (18)
It will appear in The output that appears at this calculation output terminal (Ilfζ) is a value that corresponds to the ratio of photovoltaic currents of the light receiving elements (7a) (?b), and as a result, distance information to the object to be measured (8 to (8b)) is obtained. will be obtained.

Next, let's look at the conventional light receiving device in a rangefinder configured with fζ like this! (8a) (sb) + will be explained based on FIG. Both light receiving devices @ (a a) (s b) have the same circuit configuration, so Fig. 5 shows one light receiving device a (81). In Fig. 5, (7) has the cathode at the reference potential point. Vref+ζ contact, n-type light receiving element,
u9 is n whose base is connected to the anode of this light receiving element.
The signal amplifying transistor (■) consisting of a pn transistor is an AC signal bypass capacitor connected between the emitter of this signal amplifying transistor and the ground, and the pnp (pnp) transistor constituting a current mirror circuit is connected between the emitter of this signal amplifying transistor and the ground.
The emitter of 10,000 pnp transistors is the power supply point V
cc, and its pace and collector are connected to the collector of the signal amplifying transistor u9, and the emitter of the other pnp transistor (support) is connected to the power supply point Vcc, and its base is connected to the pnp transistor υ. It is connected to the base. The device is a logarithmic compression diode connected between the collector of the pnp transistor @ of this current mirror circuit and the ground, and is composed of a diode-connected npn transistor, and the anode of the logarithmic compression diode is connected to this light receiving device. The output terminal (9) Iζ is connected. (c) Is the above power supply? This is a bias current source connected between the first point Vcc and the base of the signal amplification transistor t191, and is made up of, for example, a transistor. (2) is an NPN transistor for absorbing direct current, which is connected between the base of the signal amplification transistor u9 and the ground, and whose base is connected to the emitter of the signal amplification transistor III; the penalty is the signal amplification transistor u! A constant current source that sets the circuit bias is connected between the emitter of 1 and ground, and is composed of, for example, a transistor. (to) is the inverting input terminal (2
8a), non-inverting input end (2s b), output end (28c)
and a control terminal (28), an inverting input terminal (28a) is connected to the anode of the logarithmic compression diode @, an output terminal (28c) is connected to the inverting input terminal (28a), and the logarithmic compression diode ( c) A buffer amplifier for setting the initial ia current of (to), (to) is a capacitor connected between the control terminal (29) of this buffer amplifier and the ground, and for reducing the frequency of the buffer pump (29). )c+n@ is a constant current source, a resistor, and a diode that constitute the reference n pressure generation circuit for setting the initial voltage of the logarithmic compression diode connection υ, and the connection point between the constant current source ■ and the resistor (2) is the above Non-inverting input terminal of buffer amplifier ■ (2s b
), the constant current source ■ is composed of, for example, a transistor, and the diode ■ is a diode-connected np
n) It is composed of transistors.

The buffer amplifier (to) is configured as shown in Fig. 6fζ, in which (28c) is an npn transistor whose base is connected to the inverting input terminal 1.28a), and (280) is an npn transistor whose base is connected to the inverting input terminal 1. The collector is connected to the non-inverting input terminal (28b) and the collector is connected to the source potential point Vcc tζ,
An npn transistor whose emitter is connected to the emitter of the above npn transistor (2s e);
The transistor (2s e) constitutes a differential amplifier. (28 of these npn) transistors (
2Sa) (2sf) is a constant current source connected between the emitter connection point and ground, (28h) C28i) is a pnp transistor forming a current mirror circuit, and the emitters of both pnp transistors are connected to the power supply potential point Vcc. The bases of the above npn transistors (28e) are connected in common, and the collectors of the above npn transistors (28h) are connected to the bases and the collectors of the above npn transistors (28e).
It transmits the differential output by the n transistors (2s e) (2s f). (2sj) (2sk) is an npn transistor that constitutes a current mirror circuit,
The emitters of both npn transistors (28j) are grounded and their Cζ bases are commonly connected; the collector of one npn transistor (28j) is connected to the base and the collector of the pnp transistor (28i);
The collector of the pn transistor (2sk) is connected to the output terminal (2sk).
8c) and connected to the inverting input terminal (2Sa) + ζ degrees.

Next, the operation of this slightly constructed light receiving device will be explained. First, when there is no signal, that is, when the pulsed signal light (4) reflected from the object to be measured is not incident on the light receiving element (7), the current flowing through the amplification transistor u9 is a constant current source □□□ Since it is determined by fζ, the remaining current after subtracting the base current of the amplification transistor U from the bias current of the bias current source (time) flows to the npn transistor (311).

In addition, when external light (light of approximately constant intensity due to sunlight and its reflected light) is incident on the light receiving element (7), a direct current photovoltaic current is generated in the light receiving element (7). It turns out.

However, most of this direct current photovoltaic current flows into the npn transistor I21A for the following reason, and the current flowing into the base of the amplification transistor u9 due to this direct current photovoltaic current can be ignored.

In other words, the DC photovoltaic current initially flows into the base of the amplification transistor (6), and the amplification factor is 11yKllfJ.
It is multiplied and flows out from the emitter of the amplification transistor u9, but since it is a direct current, it does not flow into the capacitor
It will flow into the base of transistor +2!61. As a result, the DC photovoltaic current is drawn away through the collector of the npn transistor (to) and feedback is applied, so that the amplifying transistor u! The current flowing into the base of Il is 1/(hgy d91Xhyx lA), which is very small and can be ignored.

Therefore, the current flowing into the collector of the amplification transistor Lll has a constant current value determined by the constant current source when there is no signal. A current having the same value as the current flowing into the collector flows out from the collector of the pnp transistor (2) constituting the current mirror circuit. On the other hand, the reference voltage of the reference voltage generation circuit consisting of constant current source ■, resistor 6υ and diode ■ is applied to the non-inverting input terminal of the buffer amplifier (
2s b), and the collector of the pnp transistor ■ is connected to the inverting input terminal (28a) and output terminal (28C) of the buffer amplifier, so the current flowing from the collector of the pnp transistor ■ is a logarithmic compression diode. Nono7/- potential (output terminal of buffer amplifier ■)
The current is shunted to the logarithmic compression diode (to) and the buffer amplifier (to) so that the 2s c) [orders] are equal.

Therefore, the reference voltage of the reference voltage generating circuit appears at the output terminal (9) of the light receiving device @(8).

Here, the reverse saturation current of the diode @Naru■ is Is,
The current flowing from the collector of the pnpl-rangistaro is IC, the current flowing into the logarithmic compression diode (c) is IF, the current flowing into the constant current is I (3I, resistor C31), and the resistance value of resistor C31 is R( 311, the anode potential of the logarithmic compression diode becomes 2KT I''N Q 1nIs, and the reference voltage of the reference voltage generation circuit becomes KT Iln , In, + RGII I (3ff).
This is because both pressures are equal.

On the other hand, when the pulsed signal light +41 reflected from the object to be measured is incident on the light receiving element (7), this pulsed signal light 14+ generates a pulsed photovoltaic current in the light receiving element (7). It becomes iζ to be done. This pulsed photovoltaic current is generated by the amplification transistor 1! flows into the base of i, hF,
The signal is multiplied by u* and flows from the emitter of the amplification transistor 09 to the capacitor (7). At this time, since the pulsed photovoltaic current multiplied by hFEu91 is alternating current, it does not flow into the base of the npn transistor 4, and therefore no feedback occurs.

Therefore, the current flowing into the collector Iζ of the amplification transistor ul is the current value determined on the constant current source plane and the capacitor lζ
The current value is the sum of the flowing hF and the pulsed photovoltaic current value multiplied by uCJ. The current of the same group as the current value flowing into this collector Iζ constitutes a current mirror circuit.
It will flow out from the collector of the transistor @.

On the other hand, since the capacitor (to) is connected to the control end (28a) of the buffer amplifier ■, the buffer amplifier ■ responds to the potential change Jζ at the inverting input end (28a) at the output end (2s c). As a result, the increased amount flowing from the collector of the pnp transistor 2 compared to the time of no signal, which corresponds to the pulsed photovoltaic method multiplied by hpBu9, flows into the logarithmic compression diode I241, and due to this increased amount, The anode potential of the logarithmic compression diode @ increases, and the output terminal (9) IC of the light receiving device appears.

The potential at the output end (9) at this time becomes a pulse for the light receiving element (71).

Using two light receiving devices (8) configured in this way, the fourth
The distance measuring device shown in the figure is configured. Now, the photovoltaic currents of the light receiving elements (7a) (7b) generated by the pulsed signal light (4) reflected from the object to be measured are respectively IL (7a).
), IL (7b) and root, light receiving device & (s a) (
The output ends (9a) and (9b) of sb) will appear.

Here, the light receiving device! ! (8a) Since the reference potential in the reference voltage generation circuit in (ab) is a sufficiently small value 1, I 12211. thpKL19IL(7a)
and hrBi1911 L (7b) tt, and assuming that the voltage of the reference voltage source (161 is Vs), the output of the operational amplifier q3 is as shown in the following equation.

= 'I'1nIL to v8+2 (7b)q IL
(7a Therefore, the output end (old) ζ is the light receiving element (7a) (7b)
Photogenesis 1a in +ζ accent IL (7a), lx,
A voltage corresponding to the ratio lζ of (7b) appears, and this voltage has a value that allows the distance to the object to be measured to be obtained.

[Problem that the invention seeks to solve]

In the above-mentioned light receiving device, since the anode of the light receiving element (7) is directly connected to the base of the amplification transistor ill, it is easy to receive Fyg of low frequency external light such as a fluorescent lamp. Under such circumstances fζ, errors tend to occur in the distance measurement results to the object to be measured, and the
31 (The initial current flowing through 241, that is, the current when there is no signal, is set by the reference voltage of the reference generation circuit, so the initial laminar flow changes due to the influence of temperature changes, and the linearity of the output voltage changes. It had one point in between.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a light receiving device that is less affected by low-frequency external light such as a fluorescent lamp, and is also less affected by temperature changes.

[Means for solving problems]

A light receiving device according to the present invention amplifies a pulsed electromotive current from the light receiving device with a current amplifying transistor, and a voltage corresponding to the pulsed electromotive current appears in a logarithmic compression diode element. a first current conversion circuit that connects a low-frequency attenuation capacitor between the base of the current amplification transistor and the current amplification transistor, and that receives the collector current of the current amplification transistor and outputs a current corresponding to the collector current to the logarithmic compression diode element; and a second current conversion circuit that receives the current flowing through the logarithmic compression diode element and sets the emitter current of the current amplification transistor to a value corresponding to this current.

[Effect]

In this invention, the low-frequency attenuation capacitor suppresses the transmission of low-frequency electromotive current generated from low-frequency external light from a fluorescent lamp or the like from the light receiving element to the base of the current amplification transistor. In addition to suppressing the influence of external light, the initial current flowing through the logarithmic compression diode element (ζ) is set based on the collector current and emitter current of the current amplification transistor from the first current conversion circuit and the second current conversion circuit. This suppresses the effects of temperature changes.

〔Example〕

An embodiment of the present invention will be described below based on FIG. 1. In FIG. 1, +711! The cathode is the power supply potential point V
When connected to cc+, the anode becomes the load resistance (to)
The light receiving element (T) is grounded via the low frequency attenuation capacitor (T) connected between the anode of this light receiving element and the base of the current amplifying transistor U9, the base of which is supplied with a bias voltage, and the power supply The base bias NPN) transistor connected between the potential point VCC and the base of the current amplification transistor TLL is the first current mirror circuit consisting of a pair of PNP transistors, and the emitters of both PNP transistors are Power supply potential point V
cc and their bases are commonly connected, the base and collector of one pnp transistor (21) are connected to the collector of the amplification transistor u9, and the other pnp
The collector of the np transistor ■ is connected to the anode of the logarithmic compression diode, and the collector of the pnp transistor a
The emitter area ratio of ucs is configured to 1:n and pnp
The relationship is such that the value of the current flowing through the transistor CD is n times the value of the current flowing through the transistor CD. ■
Above & l! A constant current I(
A first constant current source through which a current flows, which is composed of, for example, a transistor. (To) is an npn transistor whose base is connected to the base of the logarithmic compression diode (2) to form a current mirror circuit, and is set so that a current value equal to that of the logarithmic compression diode (To) flows.

(to) is a second current mirror circuit consisting of a pair of pnp transistors, the emitters of both pnp transistors are connected to the power supply potential point Vcclζ, and their bases are commonly connected; pnp transistor (the base and collector of the mouth are connected to the collector of the above npn transistor
) A third current mirror circuit consisting of transistors 11), in which the emitters of both transistors are grounded and their bases are commonly connected, and the base and collector of -1000 are connected to the collector of the pnp transistor 11). , npn transistor (each pnp transistor f41 so that the current value flowing through 441 [ζ is n times the current value flowing through the pnp transistor ■) f4
1) and npn) Rungis*u (4i emitter area ratio is set. +461 is a pair of np
n) A fourth current mirror circuit consisting of a run raster 0η, in which the emitters of both transistors are grounded and their bases are commonly connected, and one npn) transistor 1? The base and collector of the + transistor are connected to the collector of the pnp transistor (441) and also connected to the power supply potential point Vcc tζ via the second constant current source (c), and the collector of the other transistor decoy is connected to the collector of the current amplifying transistor u9. It is connected to the emitter, and is set so that equal current flows through both transistors (4). 4 is the fourth constant current source connected between the anode of the logarithmic compression diode and the ground. be.

Next, the operation Iζ of the light receiving device configured in this way will be explained. First, a description will be given of the time when the pulsed signal light (4) reflected from the object to be measured is not incident on the light receiving element (7), that is, when there is no signal. Now, if the initial current flowing through the logarithmic compression diode (2) (to) is denoted by (to), then the pnp transistor of the first current mirror circuit (to) @
The current flowing in is (2) + I 149, which is pnp
What is the current flowing through the transistor υ? (Icy IW91
). A current of I@+ (I1f49) flows into the collector of the current amplifying transistor ul.

In addition, the transistor (to) has a current I equal to the initial current.
Q3 flows, and the second and third current mirror circuits (towards)
(Company), the third current mirror circuit (4×5 NPN) transistor circle has mI (23
A current will flow. Since a current of ml- flows through the npn transistor η of the fourth current mirror circuit 14119, a current of 114S'-mIq also flows through the npn transistor (c). Therefore, the current flowing out from the emitter of the return current amplifying transistor U) is 10,000 mI. Current amplification transistor tl! In J lζ, the base current is almost negligible, so the erector current and emitter current match, so IO2) + (Ia + 11491) = Ir:!
In order to satisfy rF+I16-mIfJ, the area ratio Rn of the force current mirror circuit and the surface area of the first to fourth constant current sources are adjusted to satisfy rF+I16-mIfJ.
(+, I plane, I゛,, shi for the constant current value of 4 years.

The initial current I (i) of the logarithmic compression diode (c) (to) can be set by the constant described above, so it can be set arbitrarily and the design margin is It's big.

The initial current 1e in the next fζ logarithmic compression diode (c) (2)
The mechanism fζ by which the signal J) flows when there is no signal will be explained.

Now, assuming that no current is flowing through the logarithmic compression diode, the transistor ■ will be in a non-conducting state, so the third current mirror circuit (NPN of 43) will also be in a non-conducting state, and the fourth A current equal to the constant current Ifa flowing through the second constant current source (c) flows through the npn transistor 17) f41G of the current mirror circuit. And, for the pnp transistor 12υ of the first current mirror circuit (toward), l1451+IH
+I(9) current flows, pnp transistor X 9 @
+ (means that a current of n (I+4!9+Il-■ (sub)) flows) ζ. This n (l145) + I)
−■(branch)) is the constant current ■(4) flowing through the fourth constant current source
Since it is greater than 9, the logarithm compression logarithm diode @(24)
A current of n(IkenI@-icm)-■(49 will flow into lζ, and it will be stabilized at the initial current If1.On the other hand, a current of larger than the initial current If23 flows into @ of the compression diode. Then, if the current flowing through the npn transistor (44) of the third current mirror circuit (transfer) is larger than ml1231, the npn transistor 17+ta of the fourth current mirror circuit 146 becomes non-conductive. Constant current source of constant current source (to) of 1■
is larger than the second constant current source, the pnp transistor (2) @ of the first current mirror circuit also becomes non-conductive, and the current value flowing into the logarithmic compression diode f231241 is reduced, and the initial current IC23 It will become stable.

As is clear from the above, the initial voltage flowing to (to) the logarithmic compression diode is determined by the first to fourth current mirror circuits and the first to third constant current sources, and appears at the output terminal (9)lζ. The voltage is such that a stable constant voltage that is less affected by temperature changes can be obtained.

In addition, when external light such as sunlight with a certain intensity or low frequency light such as a fluorescent lamp is incident on the light receiving element (7), a direct current or low frequency electromotive force is generated in the light receiving element (7). Even if this happens, the low frequency attenuation capacitor prevents the current from being transmitted to the base of the current amplifying transistor ug1, so it does not have any effect.

-10,000, When the pulsed signal light +41 reflected from the object to be measured is incident on the light receiving element (7) (ζ, the pulsed signal light +41 f (the light receiving element (7) Iζ A photovoltaic current I1171 is generated.This pulsed photovoltaic current ILt7+ flows into the base of the current amplification transistor +11 via the load resistor ■ and the low frequency attenuation capacitor, and is hpEu9) times At this time, the constant currents from the first and second constant current sources flow into the base of the current fan transistor CI!l, which is the electromotive current hFII!!
Since it is set to be sufficiently large compared to the value multiplied by 1!1, the potential variation in the base-emitter voltage of the current amplifying transistor ul is very small, and the variation in the voltage across the load resistor ω is also very small. Therefore, almost all of the pulsed photovoltaic current ILt71 in the light receiving element (7) flows to the base of the current amplification transistor u9).

Mo and hFI! ! The photovoltaic current IL multiplied by 19 (71
flows to the bypass capacitor ■, this HP
Gu! The current corresponding to J IIJ71 is the pnp transistor @iζ current in the first current mirror circuit diagram, p
np) transistor @ l (n-hrIu!11 I L
+71 will flow. As a result, the logarithmic compression diode 1 cap ζ is 1123) + n h F K + 191 I
A current of L+71 will flow, and the output terminal Cζ
Here, an incremental pairwise compression voltage appears according to the pulsed photovoltaic current I Lt7+ of the light receiving element (7).

In the light receiving device Cζ configured as described above, a low frequency attenuation capacitor (
), the anode potential of the logarithmic compression diode plane with almost no influence can be obtained, and the initial current IL flowing through the logarithmic compression diode Cζ is changed to the first to fourth current mirror circuits 1311 (to) (conversion) 14 [9 and the first to fourth constant current sources, the anode potential of the logarithmic compression diode (c) is affected by temperature fluctuations, disturbances, etc., resulting in low accuracy. It is something.

In addition, in the above embodiment, the load resistance (to) was shown, but instead of the load resistance, a diode,
It is also possible to use a series body of a diode and a resistor, a combination of a resistor, a capacitor, and a diode, a coil, etc., which have low impedance in direct current and high impedance in alternating current.

Furthermore, in the above embodiment, the case where the light receiving device (8) is applied to one that measures the distance to a distance-measuring object has been described. It is also possible to apply the measurement equipment raIζ.

〔Effect of the invention〕

As described above, this invention connects a low frequency attenuation capacitor between the light receiving element and the base of the current amplification transistor (ζ, receives the collector current of the current amplification transistor, and generates a current corresponding to this collector current). The first current conversion circuit outputs the current i to the logarithmic compression diode element, and receives the 7g current flowing through the logarithmic compression diode element and converts this current i.
A second current conversion circuit is provided to set the emitter current of the current amplifying transistor to a value corresponding to ζ, so it is less affected by low-frequency external light such as fluorescent lights, and is less affected by temperature fluctuations. This has the effect of obtaining a logarithmic compression voltage that is hardly affected by this.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of this invention, and Figs. 2 and 3 show pulsed signal light and light receiving elements (7a) (7b).
4 is a schematic circuit diagram showing the distance measuring device, FIG. 6 is a circuit diagram showing a conventional light receiving device, and FIG. 6 is a buffer amplifier of the one shown in FIG. It is a circuit diagram showing (support). In the figure, (7) is a light receiving element, 111! i current amplification transistor, ■ is a bypass capacitor, @ (to) is a logarithmic compression diode, (5) is a second constant current source, [Yes] is a low frequency attenuation capacitor, country @ (transfer) 1461 is the first or The fourth current mirror circuit is the first and third constant current sources. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (3)

[Claims] (1) A light receiving element that generates a pulsed electromotive current in response to a pulsed signal light, a low frequency attenuation capacitor whose one electrode is connected to one end of this light receiving element, and a low frequency attenuation capacitor whose other electrode is connected to one end of this light receiving element. A current amplification transistor whose base is connected to the electrode, a bypass capacitor connected to the emitter of the current amplification transistor, and a first current conversion circuit which receives the collector current of the current amplification transistor and outputs a current corresponding to the collector current. , a logarithmic compression diode element that receives the output current of the first current exchange means, and a second current conversion that receives the current flowing through the logarithmic compression diode element and sets a value corresponding to this current as the emitter current of the current amplification transistor. A light receiving device equipped with a circuit. (2) The first current conversion means consists of a pair of transistors, one transistor is connected to the collector of the current amplification transistor, the other transistor is connected to the logarithmic compression diode, and the current value flowing through the other transistor is A first current mirror circuit having a relation that the current value flowing through one transistor is n times, and a first constant current source connected in parallel to one transistor of the first current mirror circuit. The light receiving device according to claim 1, wherein the light receiving device is a light receiving device. (3) The second current conversion means includes a logarithmic compression diode element and a transistor constituting a current mirror circuit, a second current mirror circuit consisting of a pair of transistors, one of which is connected to the transistor;
a third current mirror circuit consisting of a pair of transistors, one of which is connected to the other transistor of the second current mirror circuit; and a third current mirror circuit consisting of a pair of transistors, one of which is connected to the other transistor of the second current mirror circuit; a fourth current mirror circuit connected in parallel to the other transistor of the transistor and connected to the second constant current source, the other transistor being connected to the emitter of the current amplification transistor; and a third constant current source connected in parallel to the other transistor, so that the current value flowing through the other transistor of the fourth current mirror circuit is m times the current value flowing through the logarithmic compression diode. 3. The light receiving device according to claim 1, wherein the first to fourth transistors are set as follows.