EE40 Summer '04, Lab11
Notation for this lab:
X_{a} means X subscript a
Introduction
This is a wrap up lab. The only difficult part is to understand how to connect the power supply, that you have implemented, to the rest of the circuit.
The operational amplifiers that you are using, need a dual power supply (+Vcc,-Vcc) while what you have built has only two nodes (+Vcc, 0V). It is common practice to use two resistors for creating the reference ground like in figure 1.
Figure 1
The first step is to make sure that you build the entire circuit. Your circuit should look like in figure 2.
Figure 2
There are few things you should pay attention to. The first is the power supply connection. Using two big resistors you can generate an intermediate voltage that can be used as reference. The reference voltage will be connected all op-amps instead of ground.
Input signals can be connected between Line1 and -V (the ground of your power supply). A coupling capacitor is used at the input to eliminate the DC signal.
Pre-lab
Bring a signal source. You can use the PC that you have in the lab, but if you have something like a cd/mp3/md player that would be better. Also try to find an amplified speaker, like the speakers that are usually connected to a PC sound blaster output. I'll bring one.
Lab
Build the entire circuit. Then connect your source (cd/mp3/md player) to one of the input line. Connect the output to the speaker or headphone. Make sure to use a coupling capacitor at the output of your system. Move the pots and verify that what you observe is the desired behavior.
Report
Write a report like if you were writing a data sheet. The important properties that you have to clearly write in a table are:
- Input impedance
- Output impedance
- Bandwidth when treble and bass pots are at minimum
- Treble and bass maximum attenuation