E Determine and plot the audio amplifiers frequency response Determine midband

# E determine and plot the audio amplifiers frequency

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E. Determine and plot the audio amplifier’s frequency response. Determine midband gain, 3-dB bandwidth, critical frequencies and roll-off rate. Compare the results to the data sheet. a. Using the information above, set the gain of the amplifier to 20. b. Set the output of the frequency generator to a sine wave with amplitude of 100 mV at 1 (one) Hz. c. Complete the table below. f (Hz) ( ) in pp V ( ) out pp V Gain 1 100mV 1.685 168.5 10 100mV 1.641 164.1 100 100mV 1.684 168.4 1k 100mV 1.673 167.3 10k 100mV 1.036 103.6 100k 100mV 1.573 157.3 500k 100mV 1.563 156.3
d. With the frequency set to 1 Hz, use the oscilloscope to measure the above values and calculate the gain. Note that very low or high frequencies may be difficult to measure. e. Continue changing the input frequency by a power of 10 (10, 100, etc.) until you reach 500kHz. f. Use a piece of graph paper to plot the results. F. Connect an input circuit such as a frequency generator and a microphone and a load such as a speaker verify the operation and troubleshoot any problems. a. Prototype the advance amplifier circuit for this step. Set the gain to 20. b. Connect a frequency generator set to a sine wave at 400 mV peak and 100 Hz to the input of the circuit. Connect an 8-ohm speaker to the output of the circuit. Set 1 R to the highest value. c. Write down your observations. Record the information below.
d. Apply power and record what you hear. Slowly decrease 1 R and record any changes. Continue to decrease 1 R . Use an oscilloscope to observe the output signal. What is happening to the output waveform? The waveform should expand out and sound gets lower. e. Change the input frequency to 1 k Hz and 10 kHz and record the change. RMS stays the same, frequency increases. f. Change the frequency generator to a square wave and repeat the steps above. Record the results. RMS is the same. Peak to peak decreased. g. Remove the frequency generator and connect a dynamic microphone to the input. Test the circuit and record the results. Vary 1 R for maximum output. Can you get maximum gain from the circuit without oscillation?
Part B - More LM386 1. The LM386 may be used to amplify voice inputs. Dynamic or Condenser (Electret) microphone are two common input devices. Dynamic microphones can be connected directly to the input of the LM386 amplifier