Due date:

• Monday session - 4/27/98.
• Wednesday session -4/29/98.

Description: Digitally Controlled Audio Amplifier:

You are part of a team that will design and build an audio amplifier. Your goals have already been set. You will design and build prototypes for several important components. You are in charge of designing the amplification stage. This stage will receive an audio input signal and amplify it in order to drive a speaker. The gain will be controlled according to the digital data received from the control unit, to be designed by another member of the team. For that purpose you will design an interface according to the specifications set by the team manager. You will provide the design with a seven-segment-display unit which displays the decimal value corresponding to the digital data received. The gain of the amplifier and therefore the sound volume at the speaker, will increase from 0 to its maximum value according to the information at the input port. The amplifier will operate connected to the wall outlet.

The following specifications have already established:

• Audio input signal:
• It is a Thevenin source with Vs=0.25 Volts peak and Rs=50 Ohms.
• The frequency range is 300 to 8000 Hertz.
• Speaker:
• It can be characterized as a load RL equal to 8 Ohms.
• The amplitude of the largest signal applied to the speaker should not exceed 2.5 Volts peak .
• The speakers will be provided by your GTAs.
• Digital data:
• It is provided in 3 bit format and the levels of each bit are 0 and 5 V corresponding to logic levels 0 and 1.
• The digital data and the volume obtained from the speaker will be in one to one correspondence.
• When the data is 000 the volume will be zero and will reach its maximum at 111.
• The input port requires to have 4 connectors. Three of them will correspond to data and the remaining one will be used for the ground connection. See figure below for details on the digital port.

 Seven-segment display:

• this will display the digital data at the input port in decimal format (from 0 to 7).
• The conversion from digital to decimal will be performed by a BCD chip.
• The seven display and decoder (BCD) is extra-credit.

 Rules:

•  Project is individual.

• Report is word processed.
• All assumptions have to be well justified.
• Report should include all calculations, measurements, simulations, and clear explanation of your design.
• Slides are required for presentation.

 Grade:

• 50 % from report.
• 50 % from demonstration and oral examination (correct operation).

 Additional:

•  on-off switch
• power-on LED