I’m guessing that you saw my earlier post about EasyEDA in this thread:īut if not there’s a bit more background to it there. The spice model is available for this device (but has not gone into EasyEDA yet). To try to make a 10MHz – 20MHz bandwidth galvanically isolated (AC coupled) high impedance scope probe.įor lower frequency precision isolated DC amplification?

I’m looking at optoisolators and optocouplers at the moment because I’m tinkering around with a hybrid of this: That isn’t specified in the datasheets either. While it provides no isolation, the transfer function is identical. To make test and evaluation easy, I used a single dual op amp and only one 12V supply.

R4 is adjusted so that it drops about 2V at maximum signal level –this is very non-critical.Ĭ1 is a compensation capacitor –for faster performance, this may be adjusted down –if too low, the circuit may oscillate. Optical isolators, devices that enforce unidirectional propagation of light, are employed to protect optical systems that are sensitive to back reflections. Potentiometer R4 accommodates gross variations in the CTR (both devices). The easiest way to test performance is to connect a DVM between input and output. Adjusting R2 so that R1 + R2 ✴.7K causes the output of U2 to come close to the input voltage signal –further adjustment of R2 will trim for the difference in CTR so that the output voltage will exactly match the input voltage. At the same time the output of U3A presents a positive going signal to U2. It is also known as optoisolator, photocoupler etc. When both op amp inputs are equal, the output of U1 stops integrating. So, to avoid backward reflection of transmitted signal optical isolators are used. is referred to as optocoupling because the output from the LED circuit is coupled via light to the photo-diode circuit. Magneto-optical phase shift is effective to realize on-chip optical isolators. U3-B turns on and provides a positive going feedback signal. Optical isolators are fabricated on SOI platforms with isolation ratios of 30 and 16 dB for TM and TE mode input, respectively. At any rate, the LM358 is very inexpensive.Ī positive signal input causes the output of U1 to shift positive. There is the LM321 single op amp, but it is unpopular and comes only in the SO-23-5 SMD package. I do this because there is no DIP single device that will do the job (that I know of). An analog optical isolator (AOI) also uses an optical link between input and output, however, the input element is usually a light-emitting diode and the output element is always a photocell. I generally use the LM358 dual op amp whenever I need a single ground sensing op amp. of Silicon nanophotonics - systems consisting of optics and electronics in a single chip for low power high data computing- an on-chip optical isolator. To maintain a high voltage rating, use two single devices and match the CTR to some degree. Optical isolators and circulators rely on the breaking of Lorentz reciprocity.

While DIP optical couplers have up to about 5kV isolation capability, this circuit cannot support above about 100V or so because one of the outputs is fed back to the input amplifier –this puts the voltage isolation between adjacent pins on the device rather than across the device.

Optical isolator chip