VT83CT datasheet(44/76 Pages) PERKINELMER

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Characteristics of Analog Optical Isolators

Capacitance

The equivalent circuit for the output photocell is a resistor in parallel

with the capacitance. The capacitance arises from the topside

metallization of the electrodes which form a coplanar capacitor. The

value of this capacitance is largely determined by the size of the

ceramic base. For lower capacitance, a smaller cell is needed. The

capacitance is so small (3.0 pF, typical on catalog AOIs) that it is

negligible in most applications. However, there are applications such

as wideband or high frequency amplifiers in which the capacitance

needs to be considered. At 4.5 MHz, the video baseband frequency,

the photocell capacitive reactance is only 12 kilohms. If the phase shift

of the signal is to be kept below 10°, the highest useful cell resistance

is only 2.0 kilohms. At high AOI input drive, where the cell is drive

below 1.0 kilohm, the capacitance can increase additionally from 2 to

10 times, possibly due to distributed effects.

Summary

Analog Optical Isolators have many unique features, such as:

High input-to-output isolation.

True resistance element output.

Wide dynamic range (low “on” resistance/high “off” resistance).

Low drive current.

Low distortion.

These features are primarily dependent on which input element and

output element photoconductive material is used in the Vactrol AOI.

Thus, there is a wide variety of Vactrols to choose from for your

application.

VT83CT 数据表(PDF) 44 Page - PerkinElmer Optoelectronics