Using the test board, one 74138 Decoder chip and two 7404 Inverter chips, connect the circuit shown in Fig-3. The inputs A0, A1, A2 & E must be connected to switches to implement the various cases of the inputs. The outputs must be connected to LEDs. Connect the circuit to a power supply then complete the logic truth table shown in Table-3A, based on the knowledge that when the light is ON then the output is logic (1), and when it is OFF the output is logic (0). Disconnect the LEDs from the circuit and use the DMM to measure the output voltages, then complete the voltage table shown in Table-3B. How many enables inside this chip ? What is the function of this circuit ? Compare the circuits in Fig-2 & Fig-3.
nouraaaaa 0 Newbie Poster
Dani 4,346 The Queen of DaniWeb Administrator Featured Poster Premium Member
What is in figures 2 and 3? What is truth table 3a? What do inputs A0, A1, etc. look like? You’re only showing us 10% of the question being asked.
rproffitt 2,662 "Nothing to see here." Moderator
Must be some black box homework assignment. I used 74xx and 74xxx parts decades ago and remember this to be a 3 to 8 decoder. https://www.ti.com/lit/ds/symlink/sn54ls138-sp.pdf shows this and the truth table.
There are 2 enables.
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