Hewlett-Packard Company

David J Gampell

Ralph E Lovelace

James S Ignowski

Randall Canha

Michael D McJimsey

The present invention provides an optical isolation amplifier which generates a low-noise analog output signal linearly related to an analog input signal and which conveniently fits within a conventional 8-pin dual in-line package. The optical isolation amplifier package includes an input chip having a sigma-delta analog-to-digital (A/D) converter for converting an analog input signal to a digital signal. The sigma-delta converter is used to modulate an off-chip LED which optically transmits the signal to a photodetector on a separate output chip having an accurate optical recovery section for reproducing the transmitted signal. Also contained on the output chip is a digital-to-analog (D/A) converter for converting the digital signal to an analog output signal linearly related to the analog input signal.

Optical isolation amplifier with sigma-delta modulation

An optical transmitter/receiver pair has an integrated CMOS circuit that provides a current flow to a pre-biased solid state light emitting device (LED) in response to the presence or absence of a digital input signal. The current flow is augmented at the rising and falling edges of the input signal to enhance turn-on and turn-off speed of the LED. The LED is optically coupled to a photodiode that produces a current flow in response to illumination. The photodiode is shielded from spurious electronic noise by a transparent shield and the output of the photodiode is amplified to produce an output voltage, which is connected to a capacitively delayed voltage divider. The voltage divider generates a time delayed threshold voltage connectable along with the output voltage to the inputs of a comparator.

Growing community of inventors

Sunnyvale, CA, United States of America

David J Gampell