JP3341379B2 - First stage amplification circuit of amplification detection IC module for photodetection signal and television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a first-stage amplifier circuit for an optical detection signal amplification / detection IC module and a television receiver having the photodetection signal amplification / detection IC module.

[0002]

2. Description of the Related Art Conventionally, a remote controller transmits a remote control infrared signal modulated by a coded pulse from a carrier, and transmits the remote control infrared signal to a photo of a controlled device such as a television receiver. A detection signal of a remote control signal, which is detected by a light receiving element such as a diode and modulated by a coded pulse, is amplified and detected by an amplification detection IC module, and the obtained coded pulse signal is decoded by a decoder IC module. Decoding and controlling each unit of a controlled device such as a television receiver by the obtained control signal are performed.

A conventional example of the first-stage amplifier circuit 2 of this kind of amplification / detection IC module for light detection signals will be described below with reference to FIG. A resistor 5 is connected between the output terminal and the inverting input terminal of the operational amplifier 3. An external connection for connecting an external photodiode as an external light receiving element for detecting an optical signal modulated by a carrier-coded pulse, which is connected between the non-inverting input terminal of the operational amplifier 3 and the ground. A pad 7 as a terminal is led out. A positive electrode of a power supply 4 for applying a reverse bias to a photodiode to be connected to the pad 7 is connected to a non-inverting input terminal of the operational amplifier 3 through an _IV conversion resistor RIV, and a negative electrode thereof is grounded. Is done. From the inverting input terminal of the operational amplifier 3,
A pad 8 as an external terminal for connecting an external resistor connected to the ground is led out.

When the first-stage amplifier 2 is used, the cathode of the photodiode 10 is connected to the pad 7, the anode is grounded, and the external resistor 11 is connected to the external resistor 11 with respect to the light detection signal obtained from the photodiode 10. An external capacitor 12 having a low impedance is connected in series, and this series circuit is connected between the pad 8 and the ground.

The first-stage amplifier circuit 2 constitutes a non-inverting amplifier circuit, and its gain Av is represented by the following equation. However, the resistance value of the resistor 5 is R ₁ , the resistor 11 and the capacitor 12
, The resistance of the resistor 11 is R ₂ , the capacitance of the capacitor 12 is C, and ω is the carrier angular frequency of the received signal. Also, tan δ is
tanδ is 0.8 for a chemical capacitor and 0.2 for a chip capacitor.

[0006]

[Equation 1] Av = 1 + R ₁ / Z where Z is Z = {[{R ₂ + tan δ · (1 / ωC ₁ )} ²
+ (1 / ωC ₁ ) ² ].

From the equation (1), it can be seen that the gain of the first-stage amplifier circuit 2 is significantly reduced due to the presence of the capacitor 12 for a signal component having a frequency sufficiently lower than the carrier frequency of the signal received by the photodiode 10. I understand.

When the impedance of the capacitor 12 is neglected, the gain Av of the first-stage amplifier circuit 2 is expressed by the following equation.

[0009]

[Number 2] _{Av = 1 + R 1 / R} 2

The variation in the resistance value of the resistor 5 in the IC is about ± 20%, and the variation in the resistance value of the external resistor 11 is about ± 10%.

[0011]

The first-stage amplifier circuit 2 of the conventional photodetection signal amplification detection IC module is for connecting an external resistor connected between the inverting input terminal of the operational amplifier 3 and the ground. Since the external terminal 8 is derived, the gain can be arbitrarily set by selecting the resistance value of the external resistor 11 connected between the external terminal 8 and the ground. is there.

However, on the other hand, since there is no correlation between the variation in the resistance value of the resistor 5 in the IC and the variation in the resistance value of the external resistor 11, there is a disadvantage that the gain of the first-stage amplifier circuit 2 greatly varies. is there.

The first-stage amplifier circuit 2 of the photodetection signal amplification / detection IC module includes a photodetection signal amplification / detection IC.
A significant portion (eg, 47 dB) of the overall gain (eg, 80 dB) in the module. If the gain of the first-stage amplifier circuit 2 is too small, the light detection signal (the carrier frequency is
Level of 40 kHz) is significantly different but in accordance with the distance between the photodiode 10 and the remote controller, at least, for example, needs to be amplified to the level required for optical detection signal in the range of 20μV _pp ~2.5V _pp There is. If the level of the photodetection signal from the photodiode 10 is low, a pulse signal of a sufficient level cannot be obtained, and if the gain of the first-stage amplifier circuit 2 is too large, oscillation may be caused. It is necessary to set the gain within a range, but if the gain of the first-stage amplifier circuit 2 varies greatly, the gain cannot be kept within an appropriate range. In some cases, the gain of the first-stage amplifier circuit 2 needs to be set arbitrarily even if the gain varies to some extent, and in other cases, the gain must be small even if the gain cannot be set arbitrarily.

In view of the above, the present invention arbitrarily selects between a case where the gain variation is large but the gain can be set arbitrarily and a case where the gain cannot be set arbitrarily but the gain variation can be reduced. An object of the present invention is to propose a first-stage amplifier circuit of an amplification detection IC module for a photodetection signal that can be used. Also, the present invention provides a first-stage amplifier that can arbitrarily select between a case where the gain variation is large but the gain can be set arbitrarily and a case where the gain cannot be set arbitrarily but the gain variation can be reduced. An object of the present invention is to propose a television receiver having a photodetection signal amplification detection IC module having a circuit.

[0015]

According to the present invention, a first-stage amplifier circuit of an optical detection signal amplification / detection IC module according to the present invention includes an operational amplifier, and a first amplifier formed in the IC between an output terminal and an inverting input terminal of the operational amplifier. And a first external connection for connecting an external light receiving element for detecting an optical signal whose carrier is pulse-modulated, which is connected between the first resistor and the non-inverting input terminal of the operational amplifier and the ground. A second external terminal for connecting an external resistor connected to the ground is derived from the inverting input terminal of the operational amplifier, and the above-mentioned is derived from the inverting input terminal of the operational amplifier. I
C through a second resistor formed in C.
Are derived from the external terminals. A television receiver according to the present invention includes an operational amplifier, a first resistor formed in an IC is connected between an output terminal and an inverting input terminal of the operational amplifier, and a non-inverting input terminal of the operational amplifier. A first external terminal for connection of an external light receiving element for detecting an optical signal whose carrier is pulse-modulated, which is connected between the ground and the ground, is led out. A second external terminal for connecting an external resistor is connected between the operational amplifier and an inverting input terminal of the operational amplifier. The second external terminal is connected to a second resistor formed in the above-described IC. A first-stage amplifier circuit of an amplification and detection IC module for a photodetection signal having a third external terminal led out is provided.

[0016]

According to the first-stage amplifier circuit of the photodetection signal amplification detection IC module of the present invention, the light receiving element is connected between the first external terminal and the ground, and the external device is connected between the second external terminal and the ground. Connect a resistor or a capacitor connected in series with a capacitor exhibiting low impedance to the light detection signal from the light receiving element, or connect the third external terminal directly, or the light detection signal from the light receiving element. To the ground through a capacitor that exhibits low impedance to According to the first-stage amplifier circuit of the photodetection signal amplification detection IC module provided in the television receiver of the present invention, the light receiving element is connected between the first external terminal and the ground, and the second external terminal and the ground are connected. Connect an external resistor or a capacitor in which a capacitor exhibiting low impedance to the light detection signal from the light receiving element is connected in series, or connect the third external terminal directly or from the light receiving element. Is grounded through a capacitor having a low impedance with respect to the light detection signal.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1, and portions corresponding to those of FIG. The carrier (the frequency is
For example, an infrared signal for remote control modulated by a coded pulse of 40 kHz) is transmitted, and the infrared signal for remote control is transmitted to a photodiode 10 as a photodetector on a controlled device such as a television receiver. Remote control signal detection signal (20 μV _{pp to} 2.5 V _pp ) detected and modulated by carrier coded pulse
Is amplified and detected by the amplification detection IC module 1, and the obtained coded pulse signal is decoded by the decoder IC module (not shown), and each part of a controlled device such as a television receiver is controlled by the obtained control signal. I do. The gain of the amplification detection IC module 1 is, for example, 80 dB.
In this case, the gain of the first-stage amplifier circuit 2 is, for example, 4
7 dB.

Next, the configuration of the first-stage amplifier circuit 2 of the amplification and detection IC module 1 will be described. The first resistor 5 is connected between the output terminal and the inverting input terminal of the operational amplifier 3. A first external terminal (pad) for connecting an external light receiving element (photodiode) for detecting an optical signal whose carrier is pulse-modulated, which is connected between the non-inverting input terminal of the operational amplifier 3 and the ground. ) 7 is derived. The positive electrode of the power supply 4 for applying a reverse bias to the photodiode 10 is connected to the non-inverting input terminal of the operational amplifier 3 through the _IV conversion resistor RIV, and the negative electrode is grounded. A second external terminal (pad) 8 for connecting an external resistor connected between the inverting input terminal of the operational amplifier 3 and the ground.
And a third external terminal (pad) 9 for grounding is derived from the inverting input terminal of the operational amplifier 3 through the second resistor 6.

Referring to FIG. 2, a use state 1 of the embodiment will be described. The cathode of the photodiode 10 is connected to the pad 7, and the anode is grounded. The pad 9 is grounded through an external capacitor 13 having a low impedance with respect to the light detection signal from the photodiode 10.

In this case, the gain of the first-stage amplifier circuit 2 is fixed by the resistance values of the resistors 5 and 6 and the capacitance of the capacitor 13, and cannot be set arbitrarily.
Since the error rates of the resistance values of
From the equation (2), the variation of the gain becomes very small. Note that, due to the presence of the capacitor 13, for a signal component having a frequency sufficiently lower than the carrier frequency of the reception signal of the photodiode 10, the gain of the first-stage amplifier circuit 2 is obtained from the above-mentioned equation (equation 1) of the first-stage amplifier circuit 2. It can be seen that the gain is significantly reduced.

Referring to FIG. 3, a use state 2 of the embodiment will be described. The cathode of the photodiode 10 is connected to the pad 7, and the anode is grounded. External resistor 11
, An external capacitor 12 exhibiting a low impedance to the light detection signal from the photodiode 10 is connected in series, and this series circuit is connected between the pad 7 and the ground.

In this case, the gain of the first-stage amplifier circuit 2 can be arbitrarily set by selecting the resistor 11 having an arbitrary resistance value. However, since there is no correlation between the variation in the resistance value of the resistor 5 in the IC and the variation in the resistance value of the external resistor 11, the variation in the gain of the first-stage amplifier circuit 2 increases. Note that the presence of the capacitor 12 greatly increases the gain of the first-stage amplifier circuit 2 for the signal component having a frequency sufficiently lower than the carrier frequency of the received signal of the photodiode 10 according to the above-described equation of the first-stage amplifier circuit 2. Become smaller.

In the above-described embodiment, the remote controller transmits a remote control infrared signal modulated by a pulse in which the carrier is coded, and transmits the remote control infrared signal to a controlled device such as a television receiver. A detection signal of a remote control signal, which is detected by a light receiving element such as a photodiode on the device side and modulated by a pulse in which a carrier is coded, is amplified and detected by an amplification detection IC module, and the obtained coded pulse signal is obtained. This is a case where each component of a controlled device such as a television receiver is controlled by a control signal obtained by decoding with a decoder IC module.
The infrared signal to be transmitted is not limited to the control signal, and may be a simple transmission signal.

[0024]

According to the present invention described above, the second external terminal for connecting an external resistor connected to the ground is derived from the inverting input terminal of the operational amplifier. By connecting an external resistor between the second external terminal and the ground, the gain of the operational amplifier can be arbitrarily varied (first effect), and the first and second resistors can be connected to the same IC.
And the second resistor is connected between the second and third external terminals, so that the gain of the operational amplifier cannot be arbitrarily changed, but the variation in gain can be reduced. (Second Effect) In addition, only one IC is required for obtaining the first and second effects, and there is no need to provide a separate IC, thereby meeting the needs of a plurality of users who have different needs. It is possible to obtain a first-stage amplifier circuit of a photodetection signal amplification detection IC module that can respond (third effect). Further, according to the present invention, the second external terminal for connecting an external resistor connected to the ground is derived from the inverting input terminal of the operational amplifier.
By connecting an external resistor between the external terminal and the ground, the gain of the operational amplifier can be arbitrarily varied (first effect), and the first and second resistors can be connected within the same IC. , And the second resistor is connected between the second and third external terminals, so that the gain of the operational amplifier cannot be arbitrarily varied, but the variation in gain can be reduced ( Second effect) In addition, the number of ICs for obtaining the first and second effects is one, and there is no need to provide a separate IC, thereby meeting the needs of a plurality of users who have different needs. (Third effect) It is possible to obtain a television receiver including the first-stage amplifier circuit of the photodetection signal amplification / detection IC module.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a use state 1 of the embodiment.

FIG. 3 is a circuit diagram showing a use state 2 of the embodiment.

FIG. 4 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Amplification detection IC module for light detection signals 2 First stage amplifier 3 Operational amplifier 4 Bias power supply 5 First resistor 6 Second resistor 7 Pad 8 Pad 9 Pad 10 Photodiode 11 External resistor 12 External capacitor 13 External capacitor

Claims (6)

(57) [Claims] A first resistor formed in an IC is connected between an output terminal and an inverting input terminal of the operational amplifier; and a non-inverting input terminal of the operational amplifier is connected to ground. A first external terminal for connecting an external light receiving element for detecting an optical signal whose carrier is pulse-modulated, which is connected therebetween, is derived, and is connected between the inverting input terminal of the operational amplifier and ground. A second external terminal for connecting an external resistor is led out, and a third external terminal for ground is connected to the inverting input terminal of the operational amplifier through a second resistor formed in the IC. A first-stage amplifier circuit of an amplification detection IC module for a photodetection signal, wherein terminals are led out. 2. The light detection signal according to claim 1, wherein a light receiving element is connected between the first external terminal and ground, and the third external terminal is grounded. First-stage amplifier circuit for amplification detection IC module. 3. The light detection signal according to claim 2, wherein the third external terminal is grounded through an external capacitor exhibiting a low impedance with respect to the light detection signal from the light receiving element. First-stage amplifier circuit for amplification detection IC module. 4. A light-receiving element is connected between the first external terminal and ground, and an external resistor is connected between the second external terminal and ground. Item 1. A first-stage amplifier circuit of the photodetection signal amplification detection IC module according to Item 1. 5. The photodetection signal amplifier according to claim 4, wherein an external capacitor exhibiting a low impedance with respect to the photodetection signal from the light receiving element is connected in series to the external resistor. The first-stage amplifier circuit of the detection IC module. 6. An operational amplifier, wherein a first resistor formed in an IC is connected between an output terminal and an inverting input terminal of the operational amplifier, and a non-inverting input terminal of the operational amplifier is connected to ground. A first external terminal for connecting an external light receiving element for detecting an optical signal whose carrier is pulse-modulated, which is connected therebetween, is derived, and is connected between the inverting input terminal of the operational amplifier and ground. A second external terminal for connecting an external resistor is led out, and a third external terminal for ground is connected to the inverting input terminal of the operational amplifier through a second resistor formed in the IC. A television receiver, comprising: an amplification detection IC module for a photodetection signal having a first-stage amplification circuit whose terminals are led out.