JPH0766638A - Initial stage amplifier circuit of amplification detection ic module for photodetecting signal - Google Patents

Abstract

PURPOSE:To obtain the initial stage amplifier circuit of an amplification detection IC module for photodetecting signal which is capable of arbitrarily selecting a case where the dispersion of gain is large and gain can be arbitrarily set and a case where gain can not be arbitrarily set and the dispersion of gain can be reduced. CONSTITUTION:This circuit is provided with an arithmetic amplifier 3 and a first resistor 5 is connected between the output terminal and inversion input terminal of the arithmetic amplifier 3. By the noninverted input terminal of the arithmetic amplifier 3, a first exterior terminal 7 for connecting an exterior photodetector detecting an optical signal which is connected to ground and whose carrier is pulse-modulated is derived. By the inversion input terminal of the arithmetic amplifier 3, a second exterior terminal 8 for exterior resistor connection to be connected to ground is derived. By the inversion input terminal of the arithmetic amplifier 3, a third exterior terminal 9 of ground is derived through a second resistor 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to amplification detection I for photodetection signals.
The present invention relates to a first stage amplifier circuit of a C module.

[0002]

2. Description of the Related Art Conventionally, a remote controller transmits a remote control infrared signal modulated by a carrier coded pulse, and the remote control infrared signal is transmitted to a photo control device side such as a television receiver. The detection signal of the remote control signal, which is detected by a light receiving element such as a diode and the carrier is modulated by the coded pulse, is amplified and detected by the amplification detection IC module, and the obtained coded pulse signal is decoded by the decoder IC module. Decoding and controlling each section 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 photodetection signal amplification detection IC module will be described below with reference to FIG. The resistor 5 is connected between the output terminal and the inverting input terminal of the operational amplifier 3. 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 The pad 7 as a terminal is led out. The positive electrode of the power source 4 for applying a reverse bias to the photodiode to be connected to the pad 7 is connected to the non-inverting input terminal of the operational amplifier 3 through the _IV conversion resistor R _IV , and the negative electrode thereof is grounded. To be 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 thereof is grounded, and the external resistor 11 is used to detect the light detection signal obtained from the photodiode 10. An external capacitor 12 exhibiting 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 expressed by the following equation. However, the resistance value of the resistor 5 is R ₁ , the resistor 11 and the capacitor 12 are
The impedance of the series circuit Z, the resistance value of the resistor 11 R _2, the capacitance of the capacitor 12 C, a carrier angular frequency of the received signal ω of. Also, tan δ of the capacitor 12
Tan δ is 0.8 for chemical capacitors and 0.2 for chip capacitors.

[0006]

## EQU1 ## 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), due to the presence of the capacitor 12, the gain of the first-stage amplifier circuit 2 can be significantly reduced for a signal component having a frequency sufficiently lower than the carrier frequency of the received signal of the photodiode 10. I understand.

If the impedance of the capacitor 12 is ignored, the gain Av of the first-stage amplifier circuit 2 is given by the following equation.

[0009]

[Formula 2] Av = 1 + R ₁ / R ₂

The variation in the resistance value of the internal resistor 5 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 amplification / detection IC module for photodetection signals 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, 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, so that the gain of the first-stage amplifier circuit 2 varies greatly. is there.

By the way, the first stage amplifier circuit 2 of the photodetection signal amplification / detection IC module includes the photodetection signal amplification / detection IC.
It is responsible for 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 photodetection signal from the photodiode 10 (the carrier frequency is, for example,
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, it may cause oscillation, which is appropriate by design. It is necessary to set the gain within the range, but if the gain of the first-stage amplifier circuit 2 varies widely, the gain cannot be kept within a reasonable range. There are cases where the gain of the first-stage amplifier circuit 2 needs to be set arbitrarily even if it varies a little, and cases where it is necessary that the gain has little variation even if it cannot be set arbitrarily.

In view of the above point, the present invention arbitrarily selects a case where the gain variation is large but the gain can be arbitrarily set, and a case where the gain cannot be arbitrarily set but the gain variation can be made small. The present invention intends to propose a first-stage amplifier circuit of a photodetection signal amplification detection IC module that can be used.

[0015]

The first stage amplifier circuit 2 of the photodetection signal amplification / detection IC module according to the present invention includes an operational amplifier 3, and a first resistor is provided between the output terminal and the inverting input terminal of the operational amplifier 3. External terminal for connecting an external light-receiving element for detecting an optical signal in which a carrier is pulse-modulated, which is connected to a ground from a non-inverting input terminal of the operational amplifier 3 of the operational amplifier 3. 7 is derived, and a second external terminal 8 for connecting an external resistor connected to the ground is derived from the inverting input terminal of the operational amplifier 3 and the inverting input of the operational amplifier 3 is derived. The third external terminal 9 for grounding is led out from the terminal through the second resistor 6.

[0016]

Function: The light receiving element 10 is provided between the first external terminal 7 and the ground.
Is connected between the second external terminal 8 and the ground, or an external resistor 11 or a capacitor 12 having a low impedance with respect to the light detection signal from the light receiving element 10 connected in series is connected to the external resistor 11. Alternatively, the third external terminal 9 is grounded directly or through a capacitor 13 having a low impedance with respect to the light detection signal from the light receiving element 10.

[0017]

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

Next, the structure of the first stage amplifier circuit 2 of the amplification 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 in which a 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 R _IV , and the negative electrode thereof 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 the third external terminal (pad) 9 for grounding is led out from the inverting input terminal of the operational amplifier 3 through the second resistor 6.

A usage state 1 of the embodiment will be described with reference to FIG. The cathode of the photodiode 10 is connected to the pad 7, and its anode is grounded. The pad 9 is grounded through an external capacitor 13 that exhibits 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. However, the resistors 5 and 6 in the IC are set.
Since the error rates of the resistance values of the
From the gain equation (2), the variation in the gain becomes extremely small. Due to the presence of the capacitor 13, for a signal component having a frequency sufficiently lower than the carrier frequency of the received signal of the photodiode 10, from the above-described gain equation (Formula 1) of the first-stage amplifier circuit 2, the first-stage amplifier circuit 2 It can be seen that the gain is significantly reduced.

The usage state 2 of the embodiment will be described with reference to FIG. The cathode of the photodiode 10 is connected to the pad 7, and its anode is grounded. External resistor 11
Then, an external capacitor 12 having a low impedance with respect 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 and the variation in the resistance value of the external resistor 11 in the IC, the variation in the gain of the first-stage amplifier circuit 2 becomes large. Due to the presence of the capacitor 12, the gain of the first-stage amplifier circuit 2 is significantly increased for the signal component having a frequency sufficiently lower than the carrier frequency of the received signal of the photodiode 10 from the above-described gain equation of the first-stage amplifier circuit 2. It gets smaller.

In the above-mentioned embodiment, the remote controller transmits the infrared signal for remote control which is modulated by the pulse in which the carrier is coded, and the infrared signal for remote control is controlled by the television receiver or the like. The detection signal of the remote control signal, which is detected by the light receiving element such as a photodiode on the device side and the carrier is modulated by the coded pulse, is amplified and detected by the amplification detection IC module, and the obtained coded pulse signal is obtained. This is a case in which each section of a controlled device such as a television receiver is controlled by the control signal obtained by decoding with the 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 case where the gain variation is large but the gain can be arbitrarily set and the case where the gain cannot be arbitrarily set but the gain variation can be made small can be arbitrarily set. It is possible to obtain the first-stage amplification circuit of the photodetection signal amplification detection IC module that can be selected.

[Brief description of drawings]

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

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

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

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

[Explanation of symbols]

 1 Amplification Detection IC Module for Optical Detection Signal 2 First Stage Amplifier Circuit 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 (5)

[Claims] 1. An operational amplifier is provided, a first resistor is connected between an output terminal and an inverting input terminal of the operational amplifier, and is connected between a non-inverting input terminal of the operational amplifier and ground. A first external terminal for connecting an external light receiving element for detecting an optical signal in which a carrier is pulse-modulated is derived, and an external resistor connection is connected between the inverting input terminal of the operational amplifier and ground. And a second external terminal for grounding, and a third external terminal for grounding derived from the inverting input terminal of the operational amplifier through the second resistor. First stage amplification circuit of signal amplification detection IC module. 2. The photodetection signal according to claim 1, wherein a light receiving element is connected between the first external terminal and the ground, and the third external terminal is grounded. Amplification detection IC module first stage amplification circuit. 3. The photodetection signal according to claim 2, wherein the third external terminal is grounded through an external capacitor having a low impedance with respect to the photodetection signal from the light receiving element. Amplification detection IC module first stage amplification circuit. 4. A light receiving element is connected between the first external terminal and the ground, and an external resistor is connected between the second external terminal and the ground. Item 1. The first-stage amplifier circuit of the photodetection signal amplification detection IC module according to Item 1. 5. The amplifier for photodetection signal according to claim 4, wherein the external resistor is connected in series with an external capacitor having a low impedance with respect to the photodetection signal from the light receiving element. First stage amplification circuit of detection IC module.