Driving CMOS and TTL

The comparator’s output is capable of driving CMOS and

TTL Logic circuits.

AND Gates

The comparator can be used as three input AND gate. The

operation of the gate is as follow:

The resistor divider at the inverting input establishes a refer-

ence voltage at that node. The non-inverting input is the sum

of the voltages at the inputs divided by the voltage dividers.

The output will go high only when all three inputs are high,

casing the voltage at the non-inverting input to go above that

at inverting input. The circuit values shown work for a

″0″

equal to ground and a

″1″ equal to 5V.

The resistor values can be altered if different logic levels are

desired. If more inputs are required, diodes are recom-

mended to improve the voltage margin when all but one of

the inputs are high.

OR Gates

A three input OR gate is achieved from the basic AND gate

simply by increasing the resistor value connected from the

inverting input to V

age.

A logic

″1″ at any of the inputs will produce a logic ″1″ at the

output.

ORing the Output

By the inherit nature of an open collector comparator, the

outputs of several comparators can be tied together with a

pull up resistor to V

puts goes low, the output V

DS100080-5

FIGURE 10. Driving CMOS

DS100080-6

FIGURE 11. Driving TTL

DS100080-11

FIGURE 12. AND Gate

DS100080-10

FIGURE 13. OR Gate

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