the base of Q2 which drives it into conduction and holds the output low. Check each of the conditions
through the circuit to see if they agree with the truth table results (B, Figure 3-7).
Figure 3-7. Transistorized positive AND circuit
c. Any incoming positive signals that are lower than the operating level of the high (+6 volts in
this case) will be restored to full amplitude by the circuit. For example, if two +4-volt signals are
applied to the inputs in A, Figure 3-6, the high output will be +6 volts.
d. We can replace the entire schematic for this AND circuit with a symbol and still determine
its output for any input condition. Look at the positive logic AND gate symbol in A, Figure 3-8. Now,
follow the rules of an AND gate and complete the truth table in B, Figure 3-8. If you have any
difficulty, refer to the schematic in Figure 3-7. When you complete the truth table, check your results
with the answer on Figure 3-17.
Figure 3-8. Positive AND gate and truth table
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