SEQUENTIAL CIRCUIT #1 – SIMPLE FEEDBACK

THE CIRCUIT

In the circuit above, if Q is 0, then the value of A cannot change it. If Q is 1, then the value of A can make it drop to 0 – however, then it is stuck there.

BUILDING STEPS

If you build the circuit above without following a specific order, you might see that Q will always be 0. However, if it starts with a value of 1, then you can see how it gets locked down to 0. Follow this building order:

1-Since you are using TTL chips, the inputs are set to 1 if the pins are floating. Use this to initially set Q to 1 by having both inputs floating. (So, power the chip. Connect the output of the gate to an LED and resistor and ground. The LED should light up.)

2-Then,connect input A to 1.

3-Then connect input B to Q to create the feedback loop. We should still have a value of Q that is 1.

4-Connect A to 0. Q will drop to 0.

5-Connect A to 1. Q is locked at 0.

PROJECT EXPECTATIONS

Create the circuit above.

Show Mr. Campeau how Q can get locked to zero (following the steps above).