JPH04326008A - Photoelectric conversion circuit - Google Patents

Abstract

PURPOSE:To achieve a simplification of construction and a higher detection accuracy with the curtaining of the number of circuit elements by arranging two changeover switches to switch and output a first or second photoelectric conversion current to a differential amplifier fed back negatively. CONSTITUTION:With the operation of changeover switches 11 and 12 of a switching section 13, first and second photoelectric conversion currents from a semiconductor position detector (PSD)1 are supplied to the same differential amplifier 3, capacitor 5a and resistance 5b. To achieve this, the first and second photoelectric conversion current are subjected to current-voltage conversion on the same conditions. Hence, as compared with the case of the current-voltage conversion made via a separate circuit, highly accurate voltage can be obtained to improve the detection accurate at the incoming position of light on a PDD1. This reduces the of the differential amplifier 3, the capacitor 5a and the resistor 5b to one respectively to allow the curtaining of the number of circuit elements and the lowering the number of bonding pads for external mounting and package terminals as integrated thereby achieving a simplification of construction and a higher detection accuracy.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a semiconductor position detector (
Position Sensitive Device
:PSD) This invention relates to a photoelectric conversion circuit using PSD.

0002

6 is a wiring diagram of a photoelectric conversion circuit using a conventional semiconductor position detector. As shown in FIG. 6, a cathode K of a semiconductor position detector (hereinafter referred to as PSD) 1 is used for biasing. A first anode A1 and a second anode A2 are connected to the positive terminal of a DC power source 2, the negative terminal of which is grounded, and are the first and second electrodes of the PSD 1.
are the first differential amplifier 3 and the second differential amplifier 4, respectively.
The non-inverting input terminals of both differential amplifiers 3 and 4 are both grounded, and a capacitor 5a for ripple removal is connected between the inverting input terminal and the output terminal of the first differential amplifier 3. A parallel circuit with a resistor 5b for current/voltage conversion is connected, and a capacitor 6a for ripple removal and a resistor for current/voltage conversion are similarly connected between the inverting input terminal and output terminal of the second differential amplifier 4. A parallel circuit with 6b is connected, a common terminal of a one-contact two-circuit changeover switch 8 is connected to the voltage output terminal 7, and the output terminals of both differential amplifiers 3 and 4 are connected to the first and second terminals of the changeover switch 8. 8a and 8b.

At this time, since negative feedback is applied to both differential amplifiers 3 and 4, the inverting input terminal and non-inverting input terminal of both differential amplifiers 3 and 4 are at the same potential, that is, the ground potential. Both anodes A1 and A2 are at ground potential.

[0004] When a spot light enters the PSD 1 which is reverse biased by the DC power supply 2, the photoelectric conversion current is divided in proportion to the distance from the electrical center position of the PSD 1 to the incident position of the spot light. Anode A1
The first and second photoelectric conversion currents are output from and the second anode A2, respectively, and the first photoelectric conversion current from the first anode A1 and the second photoelectric conversion current from the second anode A2 are output.
The ripples of the photoelectric conversion currents are removed by the capacitors 5a and 6a, respectively, and at the same time, they are converted into current and voltage by the resistors 5b and 6b, respectively, and the output voltages of the differential amplifiers 3 and 4 are changed to the voltage output terminal 7 by switching the changeover switch 8. Due to the characteristics of the PSD 1, the incident position of the light on the PSD 1 can be detected from the ratio of both output voltages, regardless of the magnitude of the amount of incident light.

[0005]

However, in the case of the above-mentioned conventional photoelectric conversion circuit, two differential amplifiers, two capacitors, and two resistors are required, and especially when formed using a semiconductor integrated circuit, two capacitors 5a are required. , 6a and the two resistors 5b, 6b must be externally attached, it is necessary to provide external bonding pads and provide terminals for external components as package terminals for the semiconductor integrated circuit, making the configuration complicated. Moreover, since there are a large number of external components, the relative variation in the characteristics of external components will affect the PSD.
There was a problem in that the detection accuracy of the incident position of light on 1 was lowered.

The present invention was made to solve the above-mentioned problems, and it reduces the number of circuit elements, reduces the number of external bonding pads and package terminals when integrated, and simplifies the configuration. The purpose is to improve the detection accuracy and detection accuracy.

[0007]

[Means for Solving the Problems] A photoelectric conversion circuit according to the present invention includes a semiconductor position detector that outputs first and second photoelectric conversion currents from first and second electrodes, and a semiconductor position detector that outputs first and second photoelectric conversion currents from first and second electrodes, respectively;
a switching section that is connected to a second electrode and switches and outputs the first or second photoelectric conversion current; and a negative feedback applied difference to which the first or second photoelectric conversion current from the switching section is input. A photoelectric conversion circuit characterized by comprising a dynamic amplifier.

[0008]

[Operation] In this invention, the switching section switches and outputs the first or second photoelectric conversion current from the semiconductor position detector to the differential amplifier with negative feedback. The circuit that converts the first or second photoelectric conversion current into current/voltage is now single and common, reducing the number of circuit elements compared to the past, and reducing the number of external bonding pads and package terminals when integrated. Therefore, the configuration can be simplified and the detection accuracy can be improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a wiring diagram of a first embodiment of a photoelectric conversion circuit according to the present invention.

1, the difference from FIG. 6 is that FIG.
The second differential amplifier 4, capacitor 6a, and resistor 6b in FIG. First and second change-over switches 11 and 12 of one circuit and two contacts connected to the output terminal 7 and switched in conjunction with each other are provided.
2 common terminals to the first anode A1 of PSD1, respectively.
, the second anode A2, and connect the first and second terminals 11a and 11b of the first changeover switch 11 to the inverting input terminal and non-inverting input terminal of the differential amplifier 3, respectively. First and second terminals 1 of changeover switch 12
2a and 12b are connected to the non-inverting input terminal and the inverting input terminal of the differential amplifier 3, respectively, and the switching section 13 is configured by both the changeover switches 11 and 12.

At this time, due to negative feedback by the parallel circuit of the capacitor 5a and the resistor 5b, the inverting input terminal and the non-inverting input terminal of the differential amplifier 3 are theoretically at the same potential, and P
Both anodes A1 and A2 of SD1 are at the ground potential which is the reference potential, but if the differential amplifier 3 has an input offset voltage, this input offset voltage will cause an error.
By selecting a differential amplifier with as small an input offset voltage as possible, both anodes A1 and A2 of PSD1
can be made to have the same potential.

[0012] Also, the resistor 5b allows the first
Alternatively, the second photoelectric conversion current is converted into a current/voltage, but in order to improve the efficiency of current/voltage conversion, the higher the input impedance of the differential amplifier 3, the better. It is better to use something expensive.

[0013] Both changeover switches 11 and 12 are set to the first
If the terminals are switched to the terminals 11a and 12a,
Both anodes A1 and A2 of PSD1 are connected to the inverting input terminal and non-inverting input terminal of differential amplifier 3, respectively, via both changeover switches 11 and 12.
The ripple of the first photoelectric conversion current from the anode A1 is removed by the capacitor 5a, and the first photoelectric conversion current is converted into a current/voltage by the resistor 5b.
The output voltage generated by the voltage drop caused by b appears at the voltage output terminal 7.

On the other hand, when both the changeover switches 11 and 12 are switched to the second terminals 11b and 12b, both the anodes A1 and A2 of the PSD 1 are connected to the differential amplifiers via the changeover switches 11 and 12, respectively. Since the ripple of the second photoelectric conversion current from the second anode A2 of PSD 1 is removed by the capacitor 5a, the second photoelectric conversion current is connected to the non-inverting input terminal and the inverting input terminal of the PSD 1. 5b converts the current to voltage, and resistor 5b
An output voltage generated by the voltage drop appears at the voltage output terminal 7.

At this time, by switching the changeover switches 11 and 12, the first and second photoelectric conversion currents from the PSD 1 are supplied to the same differential amplifier 3, capacitor 5a, and resistor 5b. , the second photoelectric conversion current is converted into a current/voltage, and compared to the conventional case where the current/voltage is converted through a separate circuit, a voltage with higher accuracy can be obtained, and the position of the light incident on the PSD 1 can be adjusted. It becomes possible to improve detection accuracy.

[0016] Therefore, since only one differential amplifier, capacitor, and resistor are required, the number of circuit elements can be reduced compared to the conventional method, and the number of external bonding pads and package terminals can be reduced when integrated. , it is possible to simplify the configuration and improve detection accuracy.

Next, FIG. 2 is a wiring diagram of a second embodiment of the present invention.

In FIG. 2, the difference from FIG. 1 is that the inverting input terminal and output terminal of the differential amplifier 3 are directly connected to apply negative feedback, and the non-inverting input terminal of the differential amplifier 3 and the ground are connected directly. A parallel circuit consisting of a capacitor 5a and a resistor 5b is connected to the capacitor 5a and the resistor 5b.

In this way, by connecting the parallel circuit of the capacitor 5a and the resistor 5b between the non-inverting input terminal of the differential amplifier 3 and the ground, the first Alternatively, the second photoelectric conversion current is passed through this parallel circuit to the ground, and the first or second photoelectric conversion current by the PSD 1 is converted into a current/voltage by the resistor 5b, and the inverting input of the differential amplifier 3 is output by negative feedback. Since the terminal and the non-inverting input terminal are at the same potential, the resistor 5b
The voltage drop appears as an output voltage at the voltage output terminal 7 via the voltage follower circuit.

Therefore, as in the first embodiment, it is possible to reduce the number of circuit elements, simplify the configuration, and improve detection accuracy. The external bonding pads or package terminals that should be connected are the capacitor 5a and the resistor 5.
One terminal is sufficient for connecting one end of the parallel circuit of capacitor 5a and the non-inverting input terminal of differential amplifier 3, and for connecting both ends of the parallel circuit of capacitor 5a and resistor 5b in the case of the first embodiment. It requires fewer external bonding pads or two package terminals.

FIG. 3 is a wiring diagram of a third embodiment of the present invention.

In FIG. 3, the difference from FIG. 1 is that four transmission gates 14a, 14b, 14c, 14d are controlled on and off by two clocks φ and φ bar instead of the changeover switches 11 and 12. , one end of the transmission gates 14a, 14b is connected to the first anode A1 of the PSD 1, one end of the transmission gates 14c, 14d is connected to the second anode A2 of the PSD 1, and the transmission gates 14a, 1 are connected to the second anode A2 of the PSD 1.
4d is connected to the inverting input terminal of the differential amplifier 3, and the other ends of the transmission gates 14b and 14c are connected to the non-inverting input terminal of the differential amplifier 3 to form the switching unit 14.

At this time, the transmission gate 14
a, 14c are turned on at the same time, and transmission gates 14b, 14d are turned off.
1, the first photoelectric conversion current from the first anode A1 is supplied to the inverting input terminal of the differential amplifier 3, the capacitor 5a, and the resistor 5b. The converted voltage is output.

On the other hand, the transmission gate 14b,
14d is simultaneously turned on and transmission gates 14a and 14c are turned off, the second photoelectric conversion current from the second anode A2 of the PSD 1 is transferred to the inverting input terminal of the differential amplifier 3, the capacitor 5a, and the resistor 5b.
Therefore, a voltage obtained by converting the second photoelectric conversion current into a current and a voltage is output to the voltage output terminal 7.

[0025] Therefore, effects similar to those of the first embodiment can be obtained.

Furthermore, FIG. 4 is a wiring diagram of a fourth embodiment of the present invention.

In FIG. 4, the difference from FIG. 3 is that the inverting input terminal and output terminal of the differential amplifier 3 are directly connected to apply negative feedback, and the non-inverting input terminal of the differential amplifier 3 and the ground are connected directly. A parallel circuit of a capacitor 5a and a resistor 5b is connected in this case, and in this case, the same effect as the second embodiment can be obtained, and compared to the third embodiment, the external bonding is The number of pads or package terminals can be reduced.

FIG. 5 is a wiring diagram of a fifth embodiment of the present invention.

[0029] In place of PSD1 in Fig. 1, Fig. 5(a)
As shown in FIG. 5(b), a PSD1 with the electrode structure reversed may be used, and the wiring in this case is as shown in FIG. 5(b).

That is, in FIG. 5(b), the difference from FIG. 1 is that a PS is connected to the negative terminal of the DC power supply 2 whose positive terminal is grounded.
The anode of D1 is connected to the first electrode, which is the first and second electrode.
, the second cathodes K1 and K2 are connected to the common terminal of both changeover switches 11 and 12, respectively.

Therefore, according to the configuration of FIG. 5(b), the operation is the same as that of FIG. 1 except that the direction of the photoelectric conversion current is reversed, so that the same effect as the first embodiment can be obtained. Can be done.

[0032] Also, regarding FIGS. 2, 3, and 4, FIG.
The configuration may be similar to that of the PSD 1 and DC power supply 2 in (b).

It should be noted that the configuration of the switching section is not limited to the above embodiments, and it goes without saying that when the switching section is configured with a semiconductor switch, it may be configured with a semiconductor switch other than the transmission gate. stomach.

[0034]

Effects of the Invention As described above, according to the photoelectric conversion circuit of the present invention, the switching unit allows the first
Alternatively, in order to switch and output the second photoelectric conversion current to a differential amplifier with negative feedback, the first photoelectric conversion current from the differential amplifier or switching section
, the circuit that converts the second photoelectric conversion current into current/voltage can be shared as a single circuit, the number of circuit elements can be reduced compared to the conventional method, and the number of external bonding pads or package terminals can be reduced when integrated. By sharing the differential amplifier and the like, it is possible to simplify the configuration and improve detection accuracy, making it suitable for distance measuring devices and the like.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram of a first embodiment of a photoelectric conversion circuit of the present invention.

FIG. 2 is a wiring diagram of a second embodiment of the invention.

FIG. 3 is a wiring diagram of a third embodiment of the invention.

FIG. 4 is a wiring diagram of a fourth embodiment of the invention.

FIG. 5 is a wiring diagram of a fifth embodiment of the invention.

FIG. 6 is a wiring diagram of a conventional photoelectric conversion circuit.

[Explanation of symbols]

1 PSD (semiconductor position detector) 3 Differential amplifier 13, 14 Switching section

Claims (1)

[Claims] 1. A semiconductor position detector that outputs first and second photoelectric conversion currents from first and second electrodes, respectively; A photoelectric conversion circuit comprising: a switching section that switches and outputs a photoelectric conversion current; and a differential amplifier with negative feedback to which the first or second photoelectric conversion current from the switching section is input. .