JPH0575354A - Bias circuit for avalanche photodiode - Google Patents

Abstract

PURPOSE:To obtain an optical receiver with less deterioration in the sensitivity against temperature by making the temperature characteristic of a bias voltage coincident with the temperature characteristic of an avalanche photodiode with high accuracy through a bias circuit for the avalanche photodiode. CONSTITUTION:A temperature sensor ICI and a constant voltage circuit 2 are connected to an input of a 1st operational amplifier 5 and the same temperature characteristic as that of an avalanche photodiode 9 is possessed to an output voltage by adjusting the resistance of an input resistor 3 and a feedback resistor 4. Based on the output voltage, a bias voltage having the same temperature characteristic is generated. Since the same temperature characteristic as that of the avalanche photodiode is possessed to the bias circuit, the multiple factor of the avalanche photodiode is controlled constant regardless of temperature thereby reducing the deterioration in the temperature of an optical receiver.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias circuit for an avalanche photodiode. By matching the temperature characteristic of the bias voltage with the temperature characteristic of the avalanche photodiode, the avalanche photodiode is increased in response to changes in ambient temperature. The present invention relates to a circuit which controls a magnification constant and reduces temperature deterioration of an optical receiver using an avalanche photodiode.

[0002]

2. Description of the Related Art As a conventional example, Japanese Utility Model Application No. 61-7457.
No. 9 discloses a method of temperature compensating an avalanche photodiode by using a temperature sensitive resistor.

[0003]

However, the prior art is
Since the temperature sensitive resistor and the fixed resistor are connected in series and the bias voltage is determined based on the voltage across the temperature sensitive resistor, the reference voltage is not always linear when the linear temperature sensitive resistor is used. Further, since the temperature characteristic of the temperature sensitive resistor has a variation of about 10%, there is a drawback that an error is likely to occur in the bias voltage. Therefore, a wider range (eg
-40 ℃ to + 80 ℃) It is difficult to control the error with a small error.

An object of the present invention is to provide a bias circuit for an avalanche photodiode, which is linear even in a wide temperature range and whose temperature characteristics can be set accurately.

[0005]

To achieve the above object, the present invention controls a bias voltage of an avalanche photodiode with less error by using a temperature sensor IC that is linear with respect to temperature and has less manufacturing deviation. Bias circuit for

[0006]

The temperature sensor IC and the output of the constant voltage circuit are respectively input to the operational amplifier, and the gain of the operational amplifier is changed, whereby a reference voltage having an arbitrary temperature characteristic can be created. By matching this temperature characteristic with the temperature characteristic of the avalanche photodiode, the output voltage of the bias circuit can also be matched with the temperature characteristic of the avalanche photodiode. As a result, the multiplication factor of the avalanche photodiode becomes constant regardless of the temperature, and sensitivity deterioration of the optical receiver can be reduced.

[0007]

FIG. 1 shows an embodiment of the present invention. The first operational amplifier 5 in FIG. 1 generates a reference voltage Vref. The constant voltage circuit 2 is connected to the non-inverting input of the first operational amplifier 5. Further, the output of the temperature sensor IC1 is connected to the inverting input through the input resistor 3, and the feedback resistor 4 is further connected to the output terminal. The second operational amplifier 6 generates a control voltage from the reference voltage Vref and the output of the voltage dividing resistor 8 that monitors the bias voltage of the avalanche photodiode 9. The high voltage generation circuit 7 generates a high voltage by the control voltage from the second operational amplifier 6, and biases the avalanche photodiode 9 to which the load resistor 10 is connected.

For example, the temperature sensor IC1 used in the embodiment
(Output voltage Vt) has a negative temperature characteristic of about -8mV / ℃,
When the input resistor 3 (resistance value R1) and the feedback resistor 4 (resistance value R2) are selected so as to match the temperature characteristics of the avalanche photodiode 9, the reference voltage Vref output from the first operational amplifier 5 is given by the following equation. expressed.

[0009]

[Equation 1]

Here, Vc is the output voltage of the constant voltage circuit.

The temperature characteristic ΔVref of Vref is expressed by the following equation, where the voltage change due to the temperature of the temperature sensor IC is ΔVt.

[0012]

[Equation 2]

The second operational amplifier 6 has a large gain,
If the reference voltage Vref and the output voltage from the voltage dividing resistor 9 are operated so as to be equal, the temperature characteristics of the reference voltage and the bias voltage become equal. Therefore, in order to make the multiplication factor of the avalanche photodiode constant, it is sufficient to match the temperature characteristics of the avalanche photodiode and the reference voltage.

For example, when the ambient temperature is 25 ° C., the temperature characteristic of the avalanche photodiode is 1400 ppm / ° C., and the temperature sensor I
If the output voltage of C is 1.8V, the temperature characteristic is -8mV / ° C, the output voltage of the constant voltage circuit is 2.5V, and R1 is 100kΩ, R2 is 50kΩ by calculating the formula (2).

[0015]

According to the present invention, in the bias circuit of the avalanche photodiode, the temperature characteristics of the bias circuit are accurately matched with the temperature characteristics of the avalanche photodiode by performing temperature control using the temperature sensor IC. You can As a result, the multiplication factor of the avalanche photodiode is constant regardless of temperature,
The sensitivity deterioration of the optical receiver is reduced.

[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 conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Temperature sensor IC, 2 ... Constant voltage circuit, 3 ... Input resistance, 4 ... Feedback resistance, 5 ... First operational amplifier, 6 ... Second operational amplifier, 7 ... High voltage generating circuit, 8 ... Voltage dividing resistance , 9 ... Avalanche photodiode, 10 ... Load resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 31/107 8422-4M H01L 31/10 B

Claims (1)

[Claims] 1. An avalanche photodiode, a high voltage generating circuit for applying a bias voltage to the avalanche photodiode, a voltage dividing resistor for monitoring the bias voltage, a reference voltage circuit and a voltage dividing output of the voltage dividing resistor. In a bias circuit of an avalanche photodiode including an operational amplifier for controlling the high voltage generation circuit, a temperature sensor IC is used in the reference voltage circuit to match the bias voltage with the temperature characteristic of the avalanche photodiode. Bias circuit for avalanche photodiode.