![]() Other weaknesses are the space need and the high crosstalk between several transformers of the same kind. ![]() Inductances of the transformer take their toll, leading to pulse tilt, overshoot and phase shifts – not exactly right for time-critical edges. ![]() But this cuts off the upper limit frequency of possible transformation according to Nyquist to half the frequency of the AC voltage that is used.Ī second weakness not where analog signals are concerned but in digital technology is the lacking pulse accuracy of transformers: They may be able to cover some powers of ten in the frequency range, however the typical squarewave data signals are often distorted. That can only be got around with an amplitude-modulated AC voltage that has to be demodulated following the transformer. They miss out on slowly varying signals and DC voltage. Transformers work in different versions at frequencies from a few hertz up into the gigahertz region, but they can only operate on AC voltages. Baluns, other toroidal transformers and the coreless variants of radio technology are also in the category. Whether under power as a line transformer, which has remained indispensable to date even though implemented in the meantime in switch-mode power supplies as a variant of higher frequency, or as a pure signal, data and pulse transformer – neutral transformer. Transformers have always been customary not just for voltage or current transformation but also for galvanic isolation. All variants are currently offered by the different producers. Various techniques were used in the course of time to produce galvanic isolation, starting with the classic transformer and ending with the TMR/GMR coupler as the latest option. Galvanic isolation is called for in many electronic circuits, whether in test and measurement, in field bus systems or other extensive wiring in production plant to prevent differences in potential with possibly fatal effects, whether in audio and video engineering so that no loops occur, or in medical engineering for safety reasons.ĭigital technology, supposedly so down-to-earth, also suffers from this phenomenon, as anyone will know who has joined a satellite receiver by an electric S-P/DIF connection (instead of the variant by fiberglass cable) to an amplifier, and then found that the digital sound, otherwise free from interference, disappeared every time a light switch in the house was operated. So what are the alternatives for galvanic isolation in electronics? But optocouplers are no longer fast enough for today’s data technology. This means you need to use a pull down (or up) or even a schmitt trigger to ensure the input is always at a low or high.The (infrared) light beam of an optocoupler effectively isolates high voltages. With isolators (remember, they are connected via an electrical mean, not optical), you sometimes need to make sure the input is not left floating. In reality, if you do not need the features of an isolator, then why spend the extra dollar? It may not seem like a big deal if you make small qtys, but in huge qty, a dollar more is a lot.Īlso, even if they do advertise that they can be a direct replacement to optocouplers, that is not 100% correct. Yes, they have newer and improved versions, but you still use the older ones because the designs are documented and well understood. ![]() It is the same reason why we still use those old rs232 to USB converter chips. Why do we keep using optocouplers? Because the technology is trusted and has been used for a while. You see this a lot in chips that are used for isolating rs232 or usb (Analog Devices and Linear Technology, which is now Analog Devices, make these chips). The other way is to do it with capacitive coupling. In this case, it is probably electrically coupled via a coil (think relay or transformer). Instead, an "isolator" uses electrical means. Yes, it is functionally equivalent to an optocoupler (and it is designed to actually be a pin to pin replacement), but the part you provided does not use light as the means of making the output go low or high. ![]()
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