In this laboratory exercise, you will examine a simple circuit that is frequency dependent.  There are numerous circuits that can best be thought of as having frequency dependent behavior.  For example, when you tune a radio, you are selecting a range of frequencies from which you want to extract audio signals.  In this lab exercise, you will encounter a frequency dependent circuit and explore the capabilities of that circuit - and its limitations.

        The circuit is one of the simplest possible frequency-dependent circuits, and it is really a voltage divider composed of a resistor and a capacitor.  The circuit is shown below.

v  It is claimed that if the input signal is a sine wave, then the output signal will be a sine wave.
        Is that true?  If it is true, do the following:

• Calculate how the input sine wave and the output sine wave are related, i.e.
• Determine how the amplitude of the input sine and the output sine are related.
• Determine how the phase of the input sine and the output sine are related.

        Calculating this is not a simple task, and you should read some background first.  Click here for a lesson on the origin of the magnitude change and the phase shift in this circuit.  When you understand that, do the following:

l Measure and plot the frequency response of this circuit.
       Determine whether the circuit is a low-pass filter,
       a high-pass filter or a band-pass filter.

l Determine how well the theory and your experimental
       measurements agree.
       You will need to make those measurements with an oscilloscope.

l Evaluate how well the theory predicted your measurements.

       After  you have completed the formal part of the lab (above) get a feel for what this circuit really does by doing the following.  When you are done, report on how you see this tieing in with the formal part.  Here is what to do.

Get a signal source.

Apply the signal to the circuit.

Measure the signal.

Get a signal source:  The signal source will be the output of the CD player when you play a CD.

Apply the signal to the circuit:  Same as before.

Measure the signal:  Do this yourself - with your ears.  Connect a headset to the circuit.

        Actually, there is a problem here.  A headset will load the circuit.  Try it if you don't believe.  Actually, try putting the headphones at the output of the circuit no matter what you believe.  When you are done, try this circuit.

Ideally, this circuit should not draw much current from the R-C circuit, and it should also be able to drive the headset.  In your report explain why that is so.