“Draw a 5 V three-input XOR using two cascaded 74HC86 gates: 5 V A, B, and C input sources feed the gates, and Y drives a 10 kΩ output load.”
看懂背後的決策。
U1 produces intermediate net X from A and B, and U2 combines X with C.
VDD is supplied at 5 V with node 0 as the return reference.
Separate A, B, and C sources make every logic input a connected net.
A 10 kΩ load from Y to ground gives the output a defined connected load.
Use this circuit for a 5 V CMOS three-input parity function built from a 74HC86. Verify input drive levels, fan-out, decoupling, and the specific package pinout before hardware use.
常見問題
What logic function does this circuit implement?
Y is high when an odd number of A, B, and C are high; it is a three-input XOR or odd-parity function.
Why are two 74HC86 gates used?
A 74HC86 contains two-input XOR gates, so one gate forms A XOR B and the next combines that result with C.
What is net X?
X is the intermediate output of the first XOR stage and the first input to the second stage.
Does the 10 kΩ resistor set the logic level?
No. It is an output load to ground; the 74HC86 output still actively drives Y high or low.