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PerkinElmer Optoelectronics, a leading manufacturer of analog optical isolators (AOI) for over twenty years, makes a broad range of standard parts under its trademark VACTROL®.
There are many kinds of optical isolators, but the most common is the LED/phototransistor type. Other familiar types use output elements such as light sensitive SCRs, Triacs, FETs and ICs. The major application for these silicon based devices is to provide electrical isolation of digital lines connected between different pieces of equipment. The principle of operation is very simple. When an input current is applied to the LED, the output phototransistor turns on. The only connection between the LED and phototransistor is through light - not electrically, thus the term optical isolator. These optical isolators are primarily digital in nature with fast response times for interfacing with logic gates. Rise and fall times of a few microseconds, faster for some isolators, are typical.
The analog optical isolator (AOI) also uses an optical link between input and output. The input element is an LED and the output element is always photoconductive cell or simply photocell. Together, the coupled pair acts as an electrically variable potentiometer. Since the output element of the AOI is a resistor, the voltage applied to this output resistor may be DC and/or AC and the magnitude may be as low as zero or as high as the maximum voltage rating. Because the input will control the magnitude of a complex waveform in a proportional manner, this type of isolator is an analog control element. AOIs may be used in the ON-OFF mode but the fastest response time is only in the millisecond range. A level sensitive Schmitt trigger is required between the AOI and logic gates when used in digital circuits.
Features:
- High input-to-output voltage isolation
- True resistance element output
- Single- or dual-element outputs available
- Low Cost
- Suitable for AC or DC use
- Wide range of input-to-output characteristics
- Low drive current
- Low "on" resistance, high "off" resistance
- Complete solid-state construction
LT Series
VTL5C Series
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