JPH1154738A - Photodetector/amplifier device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photodetecter/amplifier device which is capable of reducing a noise current caused by a coupling capacitance between the input terminal and output terminal of an IC chip and making an infrared receiver operate at a high speed and high in sensitivity. SOLUTION: An input signal current ipd inputted from a photodiode 3 and a noise current iCX1 generated by a coupling capacitance CX1 produced between an input wire 5 and an output wire 6 or a lead frame Vout2 are inputted into a current voltage converter/amplifier circuit 4a, a voltage outputted from the circuit 4a is inverted in phase through a current phase inverter circuit 4b to obtain an inverted input signal current ipd' and an inverted noise current iCX1' On the other hand, a dummy wire 7 whose one end is electrically open is connected to the output terminal of a current phase inverter circuit 4b through the intermediary of the dummy input terminal INd of an IC chip 4. A noise current iCX2 is generated by a coupling capacitance CX2 produced between a dummy wire 7 and the output wire 6 or the lead frame Vout2, and the noise current iCX2 is added to the inverted noise current iCX1' outputted from the current phase inverter circuit 4b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoreceiver / amplifier in an infrared receiver or the like, and more particularly to a photoreceiver / amplifier having a high-speed response and a high sensitivity.

[0002]

2. Description of the Related Art With the spread of digital infrared data communication, there has been an increasing demand for a low-cost and small-size infrared receiver for use therein. In order to manufacture such an infrared receiver, an element in which a light receiving element for infrared reception and an integrated circuit chip for amplifying a received signal and outputting a digital pulse are enclosed in one resin package is being developed. . Further, infrared receivers are required to have high sensitivity for high-speed transmission and long-distance transmission.

FIG. 9 shows an equivalent circuit block diagram of a light receiving and amplifying device 11 in a conventional infrared receiver. A light receiving element such as a photodiode 13 and an integrated circuit chip 14 (hereinafter, referred to as an IC chip 14) for receiving signal amplification processing are sealed in one resin package 11a, and the resin package 11a
The configuration is such that the photodiode 13 and the IC chip 14 are electrically connected directly by the input wires 15 inside.

The photodiode 13 is mounted on the IC chip 14.
And a current-voltage conversion amplifier circuit 14a for converting the output current from the
One end of the input wire 15 connected to the DA is connected to the input terminal IN.
It is connected to the. The current-voltage conversion amplifier circuit 14a includes an amplifier A1, and an inverting input terminal of the amplifier A1 has an input terminal I.
N and the non-inverting input terminal is grounded.

A negative feedback resistor Rf and a capacitor Cf are connected in parallel between the output terminal and the inverted input terminal of the amplifier A1 in order to obtain a desired output voltage waveform. Several amplifiers including an amplifier A2 are connected to the subsequent stage of the amplifier A1, and the inverting input terminal of each amplifier is connected to the output terminal of the preceding amplifier so that the output voltage of the preceding amplifier is input. The non-inverting input terminal is grounded. A comparator CMP for generating a pulse voltage Vp is connected to a stage subsequent to these amplifiers. An output buffer B is provided at a stage subsequent to the comparator CMP, a resistor Ro is connected to the output side thereof, and a capacitor Co is connected between one end of the resistor Ro on the side of an output terminal Vout1 described later and a ground terminal. .
The IC chip 14 is provided with a power input terminal Vcc1 for driving the IC chip 14, a ground terminal GND1, and an output terminal Vout1 for outputting a pulse output voltage Vo of the output buffer B.

The cathode PDK1 of the photodiode 13 and the IC chip 1 are placed outside the resin package 11a.
4 correspond to each of the above-mentioned output terminals, and are connected to the lead frames PDK2, Vcc2, GN
D2 and Vout2. By adopting a configuration in which the photodiode 13 and the IC chip 14 are housed in one package in this way, the signal input line can be minimized, so that it is hardly affected by electromagnetic noise from outside the resin package 11a. And the light receiving and amplifying device 1
1 itself can also be manufactured very small.

Here, the operation of the light receiving and amplifying device 11 of FIG. 9 will be described. An optical signal sent from an infrared light emitting diode of an external transmitter is received by the photodiode 13 and converted into an input signal current ipd. The input signal current ipd is inverted through the input wire 15 and the input terminal IN to the amplifier A1. Input to the input terminal and output as voltage. The voltage output from the amplifier A1 is thereafter amplified through several amplifiers including the amplifier A2, then input to the inverting input terminal of the comparator CMP, and compared with a predetermined reference voltage Vth input to the non-inverting input terminal. The pulse voltage Vp from the comparator CMP
Is output as Further, this is passed through the output buffer B, so that the pulse voltage Vp becomes the pulse output voltage V
and is output to the output terminal Vout1 of the IC chip 14 through the resistor Ro. This pulse output voltage Vo
Is applied from the lead frame Vout2 of the resin package 11a to the LSI connected to the subsequent stage through the output wire 16.

[0008]

However, in the configuration of the conventional light receiving and amplifying device 11, the coupling capacitance CX1 is generated between the input wire 15 and the output wire 16 or the lead frame Vout2 inside the resin package 11a to receive light. Since the amplifying device 11 malfunctions, it is a major obstacle to increase the speed and sensitivity of the infrared receiver.

The above will be specifically described with numerical values. Taking IrDA 1.1, which is currently a standard for infrared data communication, as an example, this method requires transmission by a digital pulse signal having a pulse width of 125 ns. In this case, the rising and falling speeds dVo / dt of the pulse output voltage Vo of the light receiving and amplifying device 11 need to be about dVo / dtｄ3 [V] / 30 [ns] = 100 [V / μs] (1) is there. When the coupling capacitance CX1 is about 1
If fF, the noise current iCX1 generated by the coupling capacitance CX1 is as follows: iCX1 = CX1 × dVo / dt = 1 [fF] × 100 [V / μs] = 100 [nA] (2)

The photodiode 1 is driven by a regular optical signal.
Since the input signal current ipd output by the output signal 3 is normally several hundred nA, the pulse output voltage Vo of the light-receiving amplifier 11 is clearly influenced by the noise current iCX1. Also, it is usually difficult to design the coupling capacitance CX1 to be less than several fF. For this reason, the structure of the light receiving and amplifying device 11 as it is becomes a major obstacle to further increase the speed and sensitivity of the infrared receiver.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned conventional problems, and has as its object to reduce noise current due to coupling capacitance between input and output terminals of an IC chip, thereby further increasing the speed of an infrared receiver. Another object of the present invention is to provide a light receiving and amplifying device capable of achieving high sensitivity.

[0012]

According to a first aspect of the present invention, there is provided a light receiving and amplifying device for converting an optical signal into a current signal and a current output from the light receiving element. An integrated circuit electrically connected to an input terminal to which a signal is input by a first wire and amplifying the current signal and outputting the amplified signal from an output terminal; and an output circuit electrically connected to the output terminal by a second wire. A light receiving and amplifying device having a lead frame, wherein the integrated circuit converts the current signal into a voltage by a first current-to-voltage conversion amplifying means, and converts an output voltage from the first current-to-voltage conversion amplifying means into a current; A current phase inverting means for inverting the phase of the current signal; and a second current / voltage converting / amplifying means for converting an output current from the current phase inverting means into a voltage. The other end of the integrated circuit is electrically connected to the input terminal of the second current-to-voltage conversion amplifier, and the other end is electrically connected to the second wire or the output lead. It is characterized by further comprising a third wire for generating a capacity between the frame and the frame.

In the above invention, the current signal from the light receiving element input to the integrated circuit through the first wire includes a regular current signal, and the coupling between the first wire and the second wire or the output lead frame. It includes a noise current generated by the capacitor (hereinafter referred to as a first noise current). The current signal obtained by adding the first noise current to the normal current signal is converted into a voltage through the first current-voltage conversion amplifying means, and this voltage is converted again into a current through the current phase inverting means and input to the integrated circuit. The phase is inverted with respect to the current signal.

On the other hand, a noise current (hereinafter, referred to as a second noise current) is generated by a coupling capacitance between the third wire and the second wire or the output lead frame, and the second noise current is a second current voltage. Before being input to the conversion amplification means, it is added to the current signal whose phase has been inverted through the current phase inversion means. Therefore, the first noise current and the second noise current whose phases are inverted cancel each other, and the current signal whose noise current has been reduced is converted into a voltage by the second current-voltage conversion amplifier and output.

According to a second aspect of the present invention, there is provided a light receiving and amplifying device according to the first aspect, wherein the first current-to-voltage converting and amplifying means and the second light receiving and amplifying device are provided.
The present invention is characterized in that the current-voltage conversion amplifying means is composed of the same element.

According to the above invention, since the first current-to-voltage conversion amplifying means and the second current-to-voltage conversion amplifying means are composed of the same element, the integrated circuit is connected from the connection point between the first wire and the integrated circuit. The impedance looking at the side is substantially equivalent to the impedance looking at the integrated circuit side from the connection point between the third wire and the integrated circuit.

According to a third aspect of the present invention, there is provided a light receiving and amplifying device according to the first or second aspect, wherein an electric connection point between the third wire and the integrated circuit is provided. And an impedance adjusting element having an impedance equal to the parasitic impedance of the light receiving element.

According to the above invention, since the impedance adjusting element having an impedance equal to the parasitic impedance of the light receiving element is added to the electrical connection point between the third wire and the integrated circuit, the first wire and the integrated circuit are added. In the frequency domain of the current signal from the light-receiving element, where the parasitic impedance of the light-receiving element occupies a large proportion of the impedance seen from the connection point with the integrated circuit side, the integration from the connection point of the first wire and the integrated circuit The impedance looking at the circuit side is substantially equivalent to the impedance looking at the integrated circuit side from the connection point between the third wire and the integrated circuit.

According to a fourth aspect of the present invention, there is provided a light receiving and amplifying device according to any one of the first to third aspects, wherein the input terminal and the first current-to-voltage conversion amplifying device are provided. A first capacitive element for flowing an AC component of the current signal between the second current-voltage conversion means and the second current-voltage conversion amplifying means between the electrical connection point between the third wire and the integrated circuit; A second capacitive element having the same capacitance as the first capacitive element is provided, while the input terminal and the first capacitive element are provided.
A DC shunt circuit for shunting the DC component of the current signal between the capacitor and the capacitive element is further provided.

According to the above-mentioned invention, the first capacitive element for flowing the AC component of the current signal from the light receiving element is provided between the input terminal of the integrated circuit and the first current-voltage conversion amplifying means. Only the AC component is input to the amplifier of the current phase inversion means. Further, the first current-voltage conversion amplifying means is provided between the electrical connection point between the third wire and the integrated circuit and the first current-voltage conversion amplifying means.
A second capacitive element having the same capacitance as the capacitive element is provided, and an impedance when the integrated circuit is viewed from a connection point between the first wire and the integrated circuit, and a connection point between the third wire and the integrated circuit. From the side of the integrated circuit becomes substantially equivalent.

Further, a DC shunt circuit for shunting the DC component of the current signal is provided between the input terminal and the first capacitive element, and the DC component of the current signal from the light receiving element flows through the DC shunt circuit. The AC component flows through the first capacitive element as described above and is input to the first current-to-voltage conversion amplifier.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] An embodiment of a light receiving and amplifying device according to the present invention will be described below with reference to FIGS.

As shown in FIG. 1, a light receiving and amplifying device 1 according to the present embodiment encloses a photodiode 3 as a light receiving element and an IC chip 4 as an integrated circuit in one resin package 1a. In the configuration 1a, the photodiode 3 and the IC chip 4 are electrically connected directly with the input wire 5 as the first wire.

The IC chip 4 is provided with an input terminal IN to which an input signal current ipd as a current signal from the photodiode 3 is input, and the anode PDA of the photodiode 3 and the input terminal IN are electrically connected by the input wire 5. Connected. The input terminal IN also serves as an input terminal of the current-voltage conversion amplifier circuit 4a. The current-voltage conversion amplification circuit 4a as the first current-voltage conversion amplification means includes an amplifier A1
The inverting input terminal of the amplifier A1 is connected to the input terminal IN, and the non-inverting input terminal is grounded. Further, in order to obtain a desired output voltage waveform between the output terminal of the amplifier A1 and the inverting input terminal,
Negative feedback resistor Rf and capacitor Cf connected in parallel
Is provided. At the subsequent stage of the amplifier A1, a current phase inversion circuit 4b as current phase inversion means including a resistor R1 and a capacitor C1 connected in parallel is provided.

A current-voltage conversion amplifying circuit 4c as a second current-voltage conversion amplifying means is provided downstream of the current phase inversion circuit 4b. The current-voltage conversion amplifying circuit 4c includes an amplifier A
2, the inverting input terminal of the amplifier A2 is connected to the output terminal of the current phase inverting circuit 4b, and the non-inverting input terminal is grounded. A negative feedback resistor R2 and a capacitor C2 are connected in parallel between the output terminal and the inverted input terminal of the amplifier A2 in order to obtain a desired output voltage waveform.

Several amplifiers (not shown) are connected to the subsequent stage of the current-voltage conversion amplifier circuit 4c, and a comparator CMP is provided downstream of these amplifiers. The inverting input terminal of the comparator CMP is connected to the output terminal of the preceding amplifier, and a predetermined reference voltage Vth is applied to the non-inverting input terminal. An output buffer B is provided at the subsequent stage of the comparator CMP, and a resistor Ro is connected to the output side thereof.
A capacitor Co is connected between one end on the out1 side and the ground terminal.

A dummy input terminal INd is provided adjacent to the input terminal IN, and a point Td in the electrically open state near the anode PDA of the photodiode 3 and the dummy input terminal INd are connected to a dummy as a third wire. They are connected by wires 7. As described later, the coupling capacitance CX
1 · CX2 closer to the same value is the noise current component noise
Therefore, it is preferable that the input terminal IN and the dummy input terminal INd, and the anode PDA and the point Td be as close to each other as possible.

The dummy input terminal INd is further connected to the inverting input terminal of the amplifier A2. One end of an impedance adjustment element 4d having an impedance equal to the parasitic impedance of the photodiode 3 is connected between the dummy input terminal INd and the inverting input terminal of the amplifier A2, and the other end is grounded. The impedance adjustment element 4d includes a capacitor Cpd having a capacitance equal to the junction capacitance of the photodiode 3 and a resistor Ri having a resistance equal to the loss resistance of the photodiode 3 connected in parallel.
Further, a resistor Rpd having a resistance equal to the series resistance of the photodiode 3 is connected in series with these combined impedances.
Are connected.

The power supply input terminal Vcc1 for driving the IC chip 4 and the ground terminal GND
1. An output terminal Vout1 for outputting the pulse output voltage Vo of the output buffer B is provided.

Out of the resin package 1a, pins connected by wires corresponding to the cathode PDK1 of the photodiode 3 and the output terminals of the IC chip 4, respectively, are connected to the lead frames PDK2, Vcc2, GND.
2 and a lead frame Vout2 as an output lead frame.

Next, the operation of the light receiving and amplifying device 1 having the above configuration will be described with reference to FIG. 2 showing the equivalent circuit of FIG.

First, when an optical signal transmitted from an external transmitter is received by the photodiode 3, the photodiode 3 converts this into an input signal current ipd. On the other hand, the input wire 5 and the output wire 6 or the lead frame V
A noise current iCX1 flowing from the output terminal Vout1 toward the input terminal IN is generated by the coupling capacitance CX1 generated between the output terminal Vout1 and the output terminal Vout1. The sum i of the input signal current ipd from the photodiode 3 and the noise current iCX1
The pd + iCX1 flows through the negative feedback resistor Rf and the capacitor Cf of the amplifier A1 to output the output voltage V (X) to the point X. This output voltage V (X) is applied to the current phase inverting circuit 4b.
Is converted into a sum ipd ′ + iCX1 ′ of the inverted input signal current ipd ′ and the inverted noise current iCX1 ′, and the inverted input signal current ipd ′ and the inverted noise current iCX1 ′ are input signal current ipd and noise current iCX1 respectively.
Are inverted.

Also, due to the coupling capacitance CX2 generated between the dummy wire 7 and the output wire 6 or the lead frame Vout2, a noise current iCX2 flowing from the output terminal Vout1 to the input terminal INd in the same phase as the noise current iCX1 is generated. I do. The inverted input signal current i
sum ipd '+ i of pd' and inverted noise current iCX1 '
The noise current iCX2 is added to CX1 ′ before being input to the current-voltage conversion amplifier circuit 4c. However, since the inverted noise current iCX1 ′ and the noise current iCX2 have phases opposite to each other, they cancel each other.

As a result, the inverted input signal current ipd ′ having the reduced noise current component is supplied to the current-voltage conversion amplifier circuit 4c.
And flows through the negative feedback resistor R2 and the capacitor C2 of the amplifier A2 to generate an output voltage V (Y) at the point Y. The output voltage V (Y) is amplified through several subsequent amplifiers, but in FIG. 2, it is amplified by one amplifier A3. The voltage output from the output terminal of the amplifier A3, that is, the comparator input voltage V (Z) at the point Z before being input to the comparator CMP is input to the inverting input terminal of the comparator CMP and to the non-inverting input terminal. The pulse voltage is compared with the applied predetermined reference voltage Vth, and as a result, the pulse voltage Vp is output to the output terminal of the comparator CMP. This pulse voltage Vp is converted into a pulse output voltage Vo through an output buffer B, then output from an output terminal Vout1 through a resistor Ro, and applied to the next-stage LSI.

Here, the relationship between the coupling capacitances CX1 and CX2 and the output voltage V (Y) of the amplifier A2 will be described below using mathematical expressions. In FIG. 2, Rf = R1, Cf =
Assuming that the rising or falling speed of the pulse output voltage Vo is dVo / dt, the input impedances of the amplifiers A1 and A2 are respectively the coupling capacitance C
Since the value is very small as compared with X1 · CX2, the following expression holds. iCX1 = −iCX1 ′ = CX1 × dVo / dt (3) Therefore, iCX1 ′ = − CX1 × dVo / dt (4) Also, iCX2 = CX2 × dVo / dt (5) and input output from the photodiode 3 The relationship between the signal current ipd and the inverted input signal current ipd ′ is as follows: ipd ′ = − ipd (6) Further, the output voltage V (Y) of the amplifier A2 is as follows: V (Y) = (ipd ′ + iCX1 ′ + iCX2) × R2 (7) When the equations (4) to (6) are substituted into the equation (7), (Y) = (− ipd−CX1 × dVo / dt + CX2 × dVo / dt) × R2 = −ipd × R2 + (CX2-CX1) × dVo / dt × R2 (8) In the equation (8), if CX1 = CX2, V (Y) = − ipd × R2 (9), and the output voltage V (Y) is not affected by the coupling capacitance CX1.

In equation (8), the noise current component is 2
The item is divided by R2, and this is defined as inoise: inoise = (CX2−CX1) × dVo / dt (10)

Specific numerical examples of the noise current component noise with respect to the values of the coupling capacitances CX1 and CX2 are shown below. Rise or fall speed d of pulse output voltage Vo
Assuming that Vo / dt is 100 [V / μs], from equation (10), when CX1 = CX2 = 0 [F], innoise = (0 [F] -0 [F]) × 100 [V / μs] = 0 [A] When CX1 = 1 [fF] and CX2 = 0 [F], innoise = (0-1 [fF]) × 100 [V / μs] = − 100 [nA] (11) CX1 = CX2 When = 1 [fF], inoise = (1 [fF] −1 [fF]) × 100 [V / μs] = 0 [A] (12) CX1 = 1 [fF], CX2 = 0.8 [fF] ], Noise = (0.8 [fF] -1 [fF]) × 100 [V / μs] = − 20 [nA] (13) CX1 = 1 [fF], CX2 = 0.5 [fF] At the time, inoise = (0.5 [fF] -1 [fF]) × 100 [V / μs] = − 50 [nA] (14) This value naturally limits the sensitivity of the infrared receiver. That is, the sensitivity of the infrared receiver is determined by the noise current component noise.

Next, referring to FIG.
Output voltage Vo for input signal current ipd from
3 to 7 show the results of simulating. In each figure, (a) shows the input signal current ipd from the photodiode 3, (b) shows the output voltages V (X) and V (Y) at the points X and Y in FIG. Comparator input voltage V (Z) at point Z and comparator CMP
Reference voltage Vth, (d) indicates the pulse output voltage Vo. Here, Rf = R1 = R2 = 50 [kΩ], Rpd
= 1 [Ω], Ro = 100 [Ω], Cf = C1 = C2 =
0.5 [pF], Cpd = 15 [pF], Co = 30
[PF], the amplification degree of the amplifier A1 is 10,000,
The amplification degree of 2 is 10000, the amplification degree of the amplifier A3 is 20,
It is assumed that the amplification degree of the comparator CMP is 1000.

The above values are substituted for the coupling capacitances CX1 and CX2. However, the effect of the impedance adjustment element 4d is ignored here.

FIG. 3 shows that when CX1 = CX2 = 0 [F],
That is, this is a simulation result in an ideal case without the coupling capacitances CX1 and CX2, and it can be seen that a normal pulse output voltage Vo is output as shown in FIG. FIG. 4 shows CX1 = 1 [fF] and CX2 = 0 [F].
In other words, the simulation result in the case where there is no dummy wire 7 is shown. In FIG. 10B, the waveform of the output voltage V (X) of the amplifier A1 is distorted by the noise current iCX1 generated by the coupling capacitance CX1, and this is It can be seen that the waveform of the pulse output voltage Vo is distorted as indicated by Pnoise in FIG. FIGS. 5 to 7 show simulation results when the dummy wire 7 is provided, and CX1 = CX2 = 1 [fF] and CX1 =
1 [fF] · CX2 = 0.8 [fF], CX1 = 1 [f
F] · CX2 = 0.5 [fF].
In FIG. 5, as shown in FIG. 5B, the amplifier A1 is controlled by the noise current iCX1 generated by the coupling capacitance CX1.
Of the output voltage V (X) is distorted, but the coupling capacitance C
Since the inverted noise current iCX1 ′ is canceled by the noise current iCX2 generated by X2, the amplifier A
The output voltage V (Y) of No. 2 has a normal waveform. Therefore, the pulse output voltage Vo also has a normal waveform as shown in FIG. 6 and 7, the values of the coupling capacitances CX1 and CX2 are different, but as shown in FIG. 6D, the pulse output voltage Vo has a substantially normal waveform, and the dummy wire 7 It can be seen that there is an effect of providing.

The waveform of the pulse output voltage Vo is not only the value of each element described above, but also the positional relationship of the elements in the resin package 1a, the lengths of the input wires 5, the output wires 6, the dummy wires 7, and the IC chip. 4 sensitivity, pulse output voltage Vo
The waveform changes depending on various conditions such as the rising and falling speeds of the data, and it is possible to make the waveform closer to an ideal waveform by setting each to the optimum condition.

When the frequency of the input signal current ipd from the photodiode 3 is high, the input impedance of the amplifiers A1 and A2 increases, which affects the magnitude of the noise currents iCX1 and iCX2. Therefore, the circuit configurations of the amplifiers A1 and A2 are made the same,
By making the values of the negative feedback resistors Rf and R2 and the capacitors Cf and C2 equal, the input signal current ipd
A1 and A1
2 can have the same input impedance. As a result, the noise currents iCX1 and iCX2 become equal, and the pulse output voltage Vo can have a normal waveform.

Further, even in the frequency region of the input signal current ipd where the parasitic impedance of the photodiode 3 increases, the parasitic impedance affects the magnitude of the noise currents iCX1 and iCX2. As described above, since the impedance adjusting element 4d having an impedance equal to the parasitic impedance is connected between the dummy input terminal INd and the inverting input terminal of the amplifier A2, the input terminal IN and the dummy The impedance when the IC chip 4 side is viewed from the input terminal INd is equal. Therefore, the noise current iCX1 · iC
X2 becomes equal, and the pulse output voltage Vo can have a normal waveform.

[Embodiment 2] Another embodiment of the light receiving and amplifying device of the present invention will be described below with reference to FIG. For convenience of explanation, components having the same functions as those shown in the drawings of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The light receiving and amplifying device 1 described in the first embodiment is
Light other than the normal light signal such as sunlight is the photodiode 3
May be irradiated in a large amount. In this case, the direct current generated in the photodiode 3 causes
The DC bias point of each internal amplifier changes. At this time, it is difficult for each amplifier to maintain the same characteristics as when there is no DC current from the photodiode 3, and the light receiving and amplifying device 1 cannot perform the operation as described in the first embodiment. For example, if the open gain of the amplifier A1 is extremely reduced by the DC current from the photodiode 3, an accurate inversion noise current iCX1 'cannot be generated, so that the expression (3) cannot be satisfied.

The light receiving and amplifying device 2 according to the present embodiment is for solving the above-mentioned problem. As shown in FIG. 8, a photodiode 3 as a light receiving element and an IC chip 4 are combined into one resin package 2a. The photodiode 3 and the IC chip 4 are electrically connected directly by the input wires 5 inside the resin package 2a.

The IC chip 4 has a capacitor CIN as a first capacitive element between the input terminal IN as an electrical connection point and the amplifier A1, a dummy input terminal INd as an electrical connection point and an inversion of the amplifier A2. A capacitor CINd as a second capacitive element having the same capacitance as the capacitor CIN is provided between the input terminal I and the input terminal I.
One end of a resistor Rb as a DC shunt circuit is connected between N and the capacitor CIN, and the other end is grounded. One end of the impedance adjustment element 4d is connected between the dummy input terminal INd and the capacitor CINd, and the other end is grounded. Other circuit elements of the IC chip 4, the photodiode 3, the input wire 5, the output wire 6, the dummy wire 7, and the lead frame PDK2.
The configurations and functions of Vcc2, GND2, and Vout2 are the same as those in the first embodiment.

The operation of the light receiving and amplifying device 2 having the above configuration will be described below.

Since the capacitor CIN is provided between the input terminal IN and the amplifier A1, the photodiode 3
DC component of the current output from the
The current flows through the resistor Rb without flowing through the N. Therefore, the normal input signal current ipd and the noise current i
CX1 is input to the amplifier A1, and the current phase inversion circuit 4
As in the first embodiment, the input signal current i
pd and the inverted input signal current ipd ′ and the inverted noise current i whose phases are inverted by the same magnitude as the noise current iCX1.
CX1 'is output. That is, the input terminal IN and the amplifier A1 are AC-coupled. A capacitor CI having the same capacitance as the capacitor CIN is provided between the dummy input terminal INd and the inverting input terminal of the amplifier A2.
Since Nd is provided, the impedance when the IC chip 4 side is viewed from the input terminal IN and the dummy input terminal INd is equal, and a noise current iCX2 having the same magnitude and the same phase as the noise current iCX1 is generated.

When the coupling capacitances CX1 and CX2 are equal,
The addition of the noise current iCX2 to the inverted noise current iCX1 'completely cancels each other out, and only the inverted input signal current ipd' in which the phase of the input signal current ipd is inverted is input to the subsequent amplifier and amplified. As a result, a pulse voltage Vp is output, and a pulse output voltage Vo having a normal waveform is output from the output terminal Vout1. When the coupling capacitances CX1 and CX2 are different from each other, the noise current iCX2 is added to the inverted noise current iCX1 'to cancel each other out to some extent. If the remaining noise current is lower than the sensitivity of the comparator CMP, the comparator C
The pulse voltage Vp output by MP is output from the output terminal Vout1 as a pulse output voltage Vo having a substantially normal waveform.

[0051]

According to the first aspect of the present invention, there is provided a light-receiving amplifier.
As described above, the light receiving element that converts an optical signal into a current signal and the input terminal to which the current signal output from the light receiving element is input are electrically connected by the first wire,
A light-receiving amplifier including an integrated circuit that amplifies the current signal and outputs the amplified signal from an output terminal; and an output lead frame electrically connected to the output terminal by a second wire, wherein the integrated circuit includes the current signal Current-voltage conversion amplifying means for converting a current into a voltage, current phase inversion means for converting an output voltage from the first current-voltage conversion amplifying means into a current and inverting the phase of the current signal, And a second current-voltage conversion amplifying means for converting an output current from the means into a voltage, one end of an electrically open state is connected to the outside of the integrated circuit, and the other end is connected to the second end of the integrated circuit. A third wire electrically connected to an input terminal of the current-voltage conversion amplifying means and generating a capacitance between the second wire and the output lead frame; It is a configuration that.

Therefore, the noise current generated by the coupling capacitance between the first wire and the second wire or the output lead frame is changed to the noise current generated by the coupling capacitance between the third wire and the second wire or the output lead frame. And a pulse output voltage having a normal waveform is output from the output terminal of the integrated circuit. Therefore, there is an effect that the speed and sensitivity of the infrared receiver using the light receiving and amplifying device can be easily increased.

According to a second aspect of the present invention, there is provided a light receiving and amplifying device according to the first aspect of the present invention.
The first current-voltage conversion amplifying means and the second current-voltage conversion amplifying means are composed of the same element.

Therefore, even when the current signal of the light receiving element has a high frequency, a noise current generated by the coupling capacitance between the first wire and the second wire or the output lead frame is generated by the third wire and the second wire or the output wire. This cancels out the noise current generated by the coupling capacitance with the lead frame for use, and produces an effect that a pulse output voltage having a normal waveform can be output from the output terminal of the integrated circuit.

According to a third aspect of the present invention, as described above, in the light receiving / amplifying apparatus according to the first or second aspect, the electrical connection point between the third wire and the integrated circuit is provided at the electrical connection point. This is a configuration in which an impedance adjustment element having an impedance equal to the parasitic impedance of the light receiving element is added.

Therefore, even when the frequency of the current signal of the light receiving element increases the parasitic impedance of the light receiving element, noise current generated by the coupling capacitance between the first wire and the second wire or the output lead frame is generated. And the noise current generated by the coupling capacitance between the third wire and the second wire or the output lead frame cancels each other out, so that a pulse output voltage having a normal waveform can be output from the output terminal of the integrated circuit. .

According to a fourth aspect of the present invention, as described above, in the light receiving / amplifying apparatus according to any one of the first to third aspects, the light receiving / amplifying apparatus is provided between the input terminal and the first current-voltage converting / amplifying means. A first capacitive element for flowing an AC component of a current signal is provided, and is equal to the first capacitive element between an electrical connection point between the third wire and the integrated circuit and the second current-voltage conversion amplifier. A second capacitive element having a capacitance is provided, and a DC shunt circuit for shunting a DC component of the current signal is further provided between the input terminal and the first capacitive element.

Therefore, even when the light receiving element includes a direct current component in the current signal due to external light such as sunlight, the light receiving and amplifying device operates normally, and a pulse output of a normal waveform is output from the output terminal of the integrated circuit. There is an effect that a voltage can be output.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a light receiving and amplifying device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an equivalent circuit of the light receiving and amplifying device.

FIG. 3 is a waveform diagram showing operation waveforms of the above-described light receiving and amplifying device when there is no coupling capacitance.

FIG. 4 is a waveform diagram showing operation waveforms of the above-described light receiving and amplifying device when there is no dummy wire.

FIG. 5 is a waveform diagram showing operation waveforms of the light receiving and amplifying device when a dummy wire is provided.

FIG. 6 is a waveform diagram showing operation waveforms of the light receiving and amplifying device in another case where a dummy wire is provided.

FIG. 7 is a waveform diagram showing operation waveforms of the above-described light receiving and amplifying device in still another case where a dummy wire is provided.

FIG. 8 is a circuit diagram showing a configuration of a light receiving and amplifying device according to another embodiment of the present invention.

FIG. 9 is a circuit diagram showing a configuration of a conventional light receiving and amplifying device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 light-receiving amplifier 2 light-receiving amplifier 3 photodiode (light-receiving element) 4 IC chip (integrated circuit) 4 a current-voltage conversion amplifier (first current-voltage conversion amplifier) 4 b current phase inverter (current phase inverter) 4 c current Voltage conversion amplification circuit (second current-voltage conversion amplification means) 4d Impedance adjustment element 5 Input wire (first wire) 6 Output wire (second wire) 7 Dummy wire (third wire) CIN capacitor (first capacitive element) CINd capacitor (second capacitive element) CX2 coupling capacitance (capacitance) IN input terminal INd dummy input terminal (electrical connection point) ipd input current signal (current signal) Rb resistance (DC shunt circuit) Vout1 output terminal Vout2 lead frame ( Output lead frame)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/04 10/06 H04N 5/335

Claims (4)

[Claims] A light receiving element for converting an optical signal into a current signal;
An integrated circuit electrically connected by a first wire to an input terminal to which the current signal output from the light receiving element is input, and amplifying the current signal and outputting the amplified signal from an output terminal;
A light receiving and amplifying device including an output lead frame electrically connected to the output terminal by a second wire, wherein the integrated circuit includes a first current-to-voltage conversion amplifying means for converting the current signal into a voltage; (1) a current phase inverting means for converting an output voltage from the current-to-voltage conversion amplifying means into a current and inverting the phase of the current signal; and a second current-voltage conversion amplifying means for converting an output current from the current phase inverting means into a voltage. And one end electrically connected to the outside of the integrated circuit, and the other end is electrically connected to an input terminal of the second current-voltage conversion amplifying means of the integrated circuit. And a third wire for generating a capacitance between the second wire and the output lead frame. 2. The first current-voltage conversion amplifying means and the second current-voltage conversion amplifying means.
2. The light receiving and amplifying device according to claim 1, wherein the current-to-voltage conversion amplifying means is constituted by the same element. 3. The device according to claim 1, wherein an impedance adjusting element having an impedance equal to a parasitic impedance of the light receiving element is added to an electrical connection point between the third wire and the integrated circuit. Light receiving amplifier. 4. A first capacitive element for flowing an AC component of the current signal between the input terminal and the first current-voltage conversion amplifying means, and an electrical connection between the third wire and the integrated circuit. A second capacitive element having a capacitance equal to that of the first capacitive element is provided between a point and the second current-voltage conversion amplifying means, and the current is supplied between the input terminal and the first capacitive element. 4. The light receiving and amplifying device according to claim 1, further comprising a DC shunt circuit for shunting a DC component of a signal.