The following figures demonstrate how to interface a TTL signal to a CMOS circuit and a CMOS circuit to a TTL input. The figures also show how to interface the two circuits if the voltage levels are incompatible.
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Figure 1: TTL-to-CMOS interfacing using pull-up resistor
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Figure 2: CMOS-to-TTL interfacing using a CMOS buffer IC
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Figure 3: TTL-to-CMOS interfacing using a transistor
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Figure 4: TTL-to-CMOS interfacing using a TLL open-collector buffer IC
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Figure 5: CMOS-to-TTL interfacing using a CMOS buffer IC
(Roger L. Tokheim, Digital Electronics, 3d ed., McGraw-Hill, New York, 1990)