Difference between revisions of "Electronics bootcamp II: feedback systems"

Time and frequency response of a feedback system

Overdamped	Critically damped
Slightly underdamped	Underdamped

1. Find the transfer function of just the RC network inside the feedback loop. Use an appropriate approximation to dramatically simplify the algebra.
2. Write an expression for the transfer function of the system in feedback as a function of the amplifier gain, G.
3. Construct and debug the feedback circuit in the diagram.
4. Connect the output of a signal generator to channel 1 of an oscilloscope and also to the input of your circuit.
5. Connect the output of your circuit to channel 2 of the oscilloscope.
6. Set the function generator to produce a 100 Hz, square wave output with an amplitude of 100 mV.
7. Adjust R_gain so that the system response is slightly overdamped.
8. Measure the frequency response of the system as you did in part 1 of the electronics bootcamp.
9. Find the transfer function, the undamped natural frequency, and the damping coefficient.
10. Plot the data and transfer function (as you did in part 1)
11. Adjust R_gain so that the circuit is critically damped and repeat steps 6-8.
    • To ensure that the system is critically damped, turn the potentiometer knob until you see a slight overshoot in the response and then turn it back until the overshoot just disappears.
12. Adjust R_gain so that the circuit is slightly underdamped (two or three overshoots) and repeat steps 6-8.
13. Adjust R_gain so that the circuit is underdamped with at least a dozen or so overshoots and repeat steps 6-8.