Linear dual detector opto-isolator circuit
AssigneeAT&T Bell Laboratories
InventorsBrian A. Basarath, Robert J. Kakalec
Life of this patent
Estimating the term…
Abstract
A signal coupling arrangement including a dual detector opto-isolator arrangement operative to transfer a sensed DC signal from an input to an output of an amplifying circuit with an isolated electrical system there between incorporates amplifiers having a specific gain set by unique calibration means and to initially preset the coupling circuitry amplification gains to assure a consistent DC current transfer and DC contrast ratio in coupling DC signals from the input to the output.
Claims8
In an amplifier circuit arrangement having at least an input amplifier, an output amplifier each having inverting and noninverting inputs and a dual detector opto-isolator including a light-emitting diode and first and second light detecting diodes and providing ground isolation between the input and output amplifier, the input amplifier circuit having an amplification gain operative for compensating for different current transfer and contrast ratios in the opto-isolator, calibration to set the amplification gain comprising the steps of
- (1) setting a voltage at an inverting input of the input amplifier to a zero value,
- (2) measuring a voltage at the noninverting input of the output amplifier,
- (3) adjusting a voltage at the noninverting input of the input amplifier according to the relation
- V.sub.2 =KV.sub.4 -1
- where K is one half an inverse of a ratio of an output voltage of the output amplifier to a voltage at its inverting input, and
- V.sub.2 is a voltage at a noninverting input of the input amplifier, and
- V.sub.4 is a voltage at a noninverting input of the output amplifier, and
- (4) adjusting the voltage at the inverting input of the input amplifier until an output voltage of the output amplifier equals a preselected fixed value.
An amplification arrangement for sensing a voltage at an input and providing a proportionate voltage thereof at an output, the input and output being ground isolated by an opto-isolator having one light emitting diode and two light detecting diodes, a first light detecting diode coupled to the output and a second light detection diode providing feedback for linearizing a gain of the opto-isolator over a temperature range, the amplification arrangement having a amplification gain value calibrated to compensate for difference in gain between the light emitting diode and the first and second light detecting diode, the amplification gain being calibrated by the steps of
- (1) determining a first voltage at an output location sharing electrical ground with the output when the voltage at an input is zero,
- (2) adjusting a second voltage at an input location sharing electrical ground with the input in accord with an algebraic relation dependent upon the first voltage, and
- (3) adjusting a third voltage at an input location to achieve a predetermined voltage at the output.
Dependencies are inferred from the claim text.