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# Photoconductive Logical Circuits

IP.com Disclosure Number: IPCOM000097121D
Original Publication Date: 1962-May-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 27K

IBM

## Related People

Spruth, W: AUTHOR

## Abstract

These photoconductor logical circuits use a combination of complementarily illuminated series and shunt photoconductive paths to achieve switching action.

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Photoconductive Logical Circuits

These photoconductor logical circuits use a combination of complementarily illuminated series and shunt photoconductive paths to achieve switching action.

In the gate circuit having photoconductors, a signal, applied to input line 1 by signal input 10, is transmitted to output line 2, if a gate signal is supplied by gate signal input 11. Light sources 3 and 4 are complementarily activated. If a gate signal is present, source 3 is active and source 4 is dark, and vice-versa if a gate signal is not present. PC 12 is arranged in light receiving relationship with source
3. When source 3 is not illuminated, PC 12 is in a high resistance state. The amount of current allowed to flow through limiting resistor 14 from voltage source 15 is small. Hence, the voltage drop across resistor 14 is small and the voltage at terminal 15 is sufficient to activate source 4. When source 3 is activated, PC 12 is changed to a low resistance state. An increased amount of current is drawn through resistor 14, decreasing the potential of point 15 to the extent that source 4 is de-activated.

Sources 3 and 4 illuminate PC's 5 and 6, and 7 and 8, respectively. PC's 5 and 7 form a first voltage divider and PC's 6 and 8 form a second voltage divider. The output of the second divider is applied to output lead 2 coupled to load 13.

When there is a gate signal present on input line 9, PC's 5 and 6 are in the low resistance state. The second PC's 7 and 8 are in the...