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Optoisolators Most optoisolators are fairly simple devices. They are an LED (Light Emitting Diode) and a photosensitive device in the same package. Current through the LED makes it emit light. The light shines on a photodiode, phototransistor or some such device changing its resistance. The photosensitive device may be a photocell that generates a voltage. It may be a Cadmium Sulfide (CdS) cell that is a light sensitive resistance. It may be a photo diode that changes its reverse biased resistance depending on the amount of light. Most of the time it is a phototransistor. Photodiodes themselves have only a limited current capability measured in microamps so we make a photo transistor by connecting the reverse biased diode between the Base and Collector of an NPN transistor. We can now have an output current that has the capability in the milliamps range. The more light the LED gives off the more minority current carriers we create in the photodiode, the lower its resistance, the more the transistor conducts and the lower the Emitter – Collector resistance. Various output devices are available. Some of the more popular ones are NPN transistors, Darlington transistors, SCRs, Triacs and FETs. The output circuits can be simple or a complex circuit analog or digital. Various input characteristics are available from a single LED, two LEDs connected backto-back, or a complex circuit. Basic characteristics Emitter characteristics We have the same basic characteristics we would have for an LED. We have a Cathodeto-Anode voltage, typical forward current and a magnitude of current the LED outputs under those conditions. If you did the LED exercises you can look at the forward voltage and tell that the LEDs most popularly used are Infrared LEDs. The photosensitive devices are more sensitive to the Infrared spectrum so IR LEDs are, dare I make the statement, ALWAYS used. We also have a question of how fast the LED can be turned on and off. This gives us part of a limitation on frequency. Usually this limitation is more restricted by how fast the detecting device can be turned on and off. The LED may be able to turn on and off fast but it matters not if the detector is slower to respond. Detector characteristics CTR (Current Transfer Ratio) is a measure of how much output current we can get for a given input (LED) current. Most of the time a given part number will have variations designated by a suffix letter that designates a CTR rating. So be mindful that not all parts with the same basic part number will necessarily operate the same under the same conditions. Relating this to our understanding of transistors this relates to the gain of the output transistor. There is more to the question that this but this is a good basic description without going into great detail. Maximum operating voltage and current. Like any other transistor the output transistor has a maximum operating voltage and current capability. Typical voltages will run less than 12 Volts and less than 10 mA. There are special devices for higher voltages and current ratings. Speed is a factor for communications applications but not for switch and lamp I/O applications. Isolation Voltage. Usually rated in the thousands of volts this is not too important in most applications we run into in the gaming industry. This is a question of how much of a difference in voltage we can have between the emitter and the detector circuits. Applications Switch and Lamp I/O. In most games we have the CPU running on a nice clean voltage of 3.3 V or 5 V. Unfortunately the environment we may be in is subject to customers that walk across a high static floor and press a button on the game. We also have higher current, higher voltage (electrically noisy) circuits driving lamps and motors. To isolate these problems from our CPU circuits we use optoisolators. The LED is a pretty sturdy creature. It can take a heavy pulse we might get from a static discharge and survive it better than digital logic does. The low-voltage low-current world of the CPU cannot drive lamps and motors, so we use an optoisolator on outputs to interface the clean simple world of the CPU from the high-power world of motors and lamps. In monitors we have a power supply section running off of the line voltage and a monitor circuit itself running off of a separate ground system. The main power transformer isolates the main monitor circuits from the line referenced ground. To provide feedback in the voltage regulator we use an optoisolator to sense the output voltage and keep the regulator on track. We may also use an optoisolator to monitor the high voltage circuit in an x-ray protection circuit to shut down the power supply in the event of a dangerous condition. P/N 4N22 4N23 4N24 4N25 4N26 4N27 4N28 4N35 4N36 4N37 4N39 4N40 6N135 6N136 6N137 6N138 6N139 CNX48U CNY117 CNY17-1 CNY17-2 CNY17-3 CNY17-4 Data Sheet 4N22 4N22 4N22 4N25 4N25 4N25 4N25 4N25 4N25 4N25 4N39 4N39 6N135 6N135 6N137 6N139 6N139 H11B1 CNY117 CNY17 CNY17 CNY17 CNY17 Pinout 4N22 4N22 4N22 4N25 4N25 4N25 4N25 4N25 4N25 4N25 4N39 4N39 6N136 6N136 6N137 6N139 6N139 H11B1 4N25 4N25 4N25 4N25 4N25 H11AA1 H11AA2 H11AA3 H11AA4 H11AA814 H11AA1 H11AA1 H11AA1 H11AA1 H11A817 H11AA1 H11AA1 H11AA1 H11AA1 H11AA814 H11A1 H11A2 H11A3 H11A4 H11A5 H11A617 H11A817 4N25 4N25 4N25 4N25 4N25 H11A817 H11A817 4N25 4N25 4N25 4N25 4N25 H11A817 H11A817 H11B1 H11B2 H11B255 H11B3 H11B815 H11B1 H11B1 H11B1 H11B1 H11B815 H11B1 H11B1 H11B1 H11B1 H11B815 H11C1 H11C2 H11C3 H11C4 H11C5 H11C6 H11D1 H11D2 H11C1 H11C1 H11C1 H11C1 H11C1 H11C1 H11D1 H11D1 4N39 4N39 4N39 4N39 4N39 4N39 4N25 4N25 H11F1 H11F2 H11F3 H11F1 H11F1 H11F1 H11F1 H11F1 H11F1 H11G1 H11G2 H11G3 H11G1 H11G1 H11G1 H11G1 H11G1 H11G1 H11L1 H11L2 H21A1 H21A2 H21A3 H21B1 H21B2 H21B3 H21L1 H21L2 H22L1 H22L2 HCPL-0201 HCPL-0211 HCPL-0452 HCPL-0453 HCPL-0454 HCPL-0466 HCPL-0500 HCPL-0501 HCPL-0600 HCPL-0601 HCPL-0611 HCPL-061A HCPL-061N HCPL-0630 H11L1 H11L1 H21A1 H21A1 H21A1 H21B1 H21B1 H21B1 H21L1 H21L1 H22L1 H22L1 HCPL-2201 HCPL-2201 6N135 6N135 HCPL-4504 HCPL-4506 6N135 6N135 6N137 6N137 6N137 HCPL-261A HCPL-261A 6N137 H11L1 H11L1 H21A1 H21A1 H21A1 H21B1 H21B1 H21B1 H21L1 H21L1 H22L1 H22L1 HCLP-2201 HCLP-2201 6N136 6N136 6N136 HCPL-4506 6N136 6N136 6N137 6N137 6N137 HCPL-261A HCPL-261A HCPL-2630 HCPL-0631 HCPL-063A HCPL-063N HCPL-0661 HCPL-0700 HCPL-0701 6N137 HCPL-263A HCPL-263A 6N137 6N139 6N139 HCPL-2630 HCPL-263A HCPL-263A HCPL-2630 6N139 6N139 HCPL-2201 HCPL-2202 HCPL-2211 HCPL-2212 HCPL-2231 HCPL-2232 HCPL-2502 HCPL-2601 HCPL-2611 HCPL-261A HCPL-261N HCPL-2201 HCPL-2201 HCPL-2201 HCPL-2201 HCPL-2201 HCPL-2201 6N135 6N137 6N137 HCPL-261A HCPL-261A HCLP-2201 HCLP-2202 HCLP-2201 HCLP-2202 HCLP-2231 HCLP-2231 6N136 6N137 6N137 HCPL-261A HCPL-261A HCPL-2630 HCPL-2631 HCPL-263A HCPL-263N HCPL-3120 HCPL-2630 HCPL-2630 HCPL-263A HCPL-263A HCPL-3120 HCPL-2630 HCPL-2630 HCPL-263A HCPL-263A HCPL-3120 HCPL-3700 HCPL-4502 HCPL-4503 HCPL-3700 6N135 6N135 HCPL-3700 6N136 6N136 HCPL-4504 HCPL-4506 HCPL-4661 HCNW135 HCNW136 HCNW137 HCNW138 HCNW139 HCNW2201 HCNW2211 HCNW2601 HCNW2611 HCNW3120 HCNW4502 HCNW4503 HCNW4504 HCNW4506 KMOC3021 KMOC3023 KMOC3041 KMOC3051 KMOC3052 KMOC3053 KMOC3062 KMOC3063 LAA110 LCA110 LCC110 HCPL-4504 HCPL-4506 6N137 6N135 6N135 6N137 6N139 6N139 HCPL-2201 HCPL-2201 6N137 6N137 HCPL-3120 6N135 6N135 HCPL-4504 HCPL-4506 MOC3021 MOC3023 MOC3041 MOC3051 MOC3052 MOC3053 MOC3062 MOC3063 LAA110 LCA110 LCC110 6N136 HCPL-4506 HCPL-2630 6N136 6N136 6N137 6N139 6N139 HCLP-2201 HCLP-2201 6N137 6N137 HCNW3120 6N136 6N136 6N136 HCPL-4506 MOC3021 MOC3021 MOC3062 MOC3021 MOC3021 MOC3021 MOC3062 MOC3062 LAA110 LCA110 LCC110 MCT2 MCT2E MCT210 MCT2200 MCT2201 MCT2202 MCT271 MCT5200 MCT5201 MCT5210 MCT5211 MCT2 MCT2 MCT2 MCT2 MCT2 MCT2 MCT2 MCT5200 MCT5200 MCT5200 MCT5200 4N25 4N25 4N25 4N25 4N25 4N25 4N25 4N25 4N25 4N25 4N25 MCT6 MCT61 MCT62 MCT9001 MCT6 MCT6 MCT6 MCT9001 MCT6 MCT6 MCT6 PS2501-2 MOC3010 MOC3021 MOC3023 MOC3010 MOC3021 MOC3023 MOC3010 MOC3021 MOC3021 MOC3030 MOC3041 MOC3051 MOC3052 MOC3053 MOC3062 MOC3063 MOC3081 MOC3082 MOC3083 MOC3030 MOC3041 MOC3051 MOC3052 MOC3053 MOC3062 MOC3063 MOC3081 MOC3081 MOC3081 MOC3030 MOC3062 MOC3021 MOC3021 MOC3021 MOC3062 MOC3062 MOC3062 MOC3062 MOC3062 MOC70P1 MOC70P2 MOC70P3 MOC71H1 MOC8080 OL810 OL811 OL812 OL813 OPI110 OPI110A OPI110B OPI110C OPI113 OPL535 OPL535-OC OPL536 OPL536-OC OPL550 OPL550-OC OPL551 MOC70P1 MOC70P1 MOC70P1 MOC71H1 H11B1 OL810 OL810 OL810 OL810 OPI110 OPI110 OPI110 OPI110 OPI110 OPL535 OPL535 OPL535 OPL535 OPL550 OPL550 OPL550 MOC70P1 MOC70P1 MOC70P1 MOC71H1 H11B1 OL810 OL810 OL810 OL810 OPI110 OPI110 OPI110 OPI110 OPI113 OPL535 OPL535-OC OPL536 OPL536-OC OPL550 OPL550-OC OPL551 OPL551-OC PS2403-1 PS2403-2 PS2403-3 PS2403-4 PS2501-1 PS2501-2 PS2501-4 PVA13N PVA1352N PVA1354N PVA2352N PVA33N PVA3324N PVA3354N PVD10 PVD1052 PVD1054 PVD13 PVD1352 PVD1354 PVD2352 PVD33 PVD3354 TIL113 OPL550 PS2403-1 PS2403-1 PS2403-1 PS2403-1 PS2501-1 PS2501-1 PS2501-1 PVA13N PVA13N PVA13N PVA33N PVA33N PVA33N PVA33N PVD10 PVD10 PVD10 PVD13 PVD13 PVD13 PVD33 PVD33 PVD33 H11B1 OPL551-OC H11A817 PS2501-2 PS2501-3 PS2501-4 H11A817 PS2501-2 PS2501-4 PVA33N PVA33N PVA33N PVA33N PVA33N PVA33N PVA33N PVD33 PVD33 PVD33 PVD33 PVD33 PVD33 PVD33 PVD33 PVD33 H11B1 4N25 VF = 1.2 V @ 10 mA (normal operating range for the LED is 5 mA to 20 mA) BVCEO = 30 V CTR = 20% VCE (SAT) = 500 mV @ IC of 500 A and IF of 10 mA TON = 2 s TOFF = 2 s Forward voltage of the LED increases with Forward Current and lower temperature. At IF of 1 mA you may not get it to turn on at all at 100 C. At IF of 10 mA you will get VF = 1.2 V at 100 C. At IF of 100 mA you will get VF = 1.35 V at 100 C. At IF of 1 mA you will get VF = 1.07 V at 25 C. At IF of 10 mA you will get VF = 1.17 V at 25 C. At IF of 100 mA you will get VF = 1.5 V at 25 C. At IF of 1 mA you will get VF = 1.2 V at -55 C. At IF of 10 mA you will get VF = 1.3 V at -55 C. At IF of 100 mA you will get VF = 1.6 V at -55 C. The black packaged devices tend to run a little lower in LED voltage than the white package at comparable conditions. CTR is a little higher in the black package. CTR peaks at around 4 mA for black package and 6 mA for the white package. TR is higher at lower at IF of 5 mA than 20 mA. Selection of RBE and R LOAD influences CTR and operating frequency. At IF of 10 mA an RBE of 10K makes the CTR only 10% of typical. At 100 K Ohms CTR is about 95% of typical. At 400K Ohms CTR is about maximum. The values for CTR are lower at lower IF and higher at higher IF.. Operation is almost impossible at 5mA and RBE of 20K. Operation is typical at RBE = 100K and IF of 20 mA. Suggested value for RBE is 100K at IF of 10 mA. Lowering it decreases CTR but improves frequency response. Lowering the value of R LOAD increases switching speeds but decreases CTR. Turn off time of a typical 2 s at R LOAD of 100 Ohms increases to 10 s with an R LOAD of 1,000 Ohms and 1 ms with an R LOAD of 100,000 Ohms. Devices in this family 4N25 – CTR of 20% at IF of 10 mA 4N26 – CTR of 20% at IF of 10 mA 4N27 – CTR of 10% at IF of 10 mA 4N28 – CTR of 10% at IF of 10 mA 4N35 – CTR of 100% at IF of 10 mA 4N36 – CTR of 100% at IF of 10 mA 4N37 – CTR of 100% at IF of 10 mA H11A1 – CTR of 50% at IF of 10 mA H11A2 – CTR of 20% at IF of 10 mA H11A3 – CTR of 20% at IF of 10 mA H11A4 – CTR of 10% at IF of 10 mA H11A5 – CTR of 30% at IF of 10 mA VCE (SAT) may differ slightly between devices within the family. TON and TOFF time may differ slightly and vary with IF . Substitution suggestions; H11A3 = H11A2 = 4N25 = 4N26 H11A4 = 4N27 = 4N28 4N35 = 4N36 = 4N37
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