Question

Barry the Biologist has asked for your help to build an amplifier and filter to take small signals from his bird sensing microphones and amplify them so that he can capture the signals on his PC. The microphone produces AC signals at varying frequencies with 10 mV magnitude. His PC requires the signals to be 1 V magnitude. The signals that Barry is interested in are above 1 kHz Hz. He would like the filter to attenuate signals at frequencies below 1 kHz. The amplifier and filter circuit is to be powered from an AC plugpack. The AC plugpack provides 12 VAC RMS at 50 Hz AC Plugpack 12 VAC RMS Amplifier and Filter 1 V To PC 10 mV magnitude magnitude Microphone

Part A:

Design the power supply component of your amplifier and filter. You will need to produce a dual-sided power supply with +10V, 0V and –10V using the 12 VAC plugpack as an AC source. Assume that your amplifier and filter will draw around 10 mA of current on both the positive and negative voltage supplies. Your design should include components to minimise voltage ripple. Show calculations for the selection of components where practical. Show a circuit diagram for the complete power supply circuit.

Part B:

Design the amplifier and filter circuit to meet Barry’s requirements. The circuit must produce the required gain, and also attenuate the signals below 1 kHz. Show calculations for the selection of components where practical. Show a circuit diagram for the complete amplifier and filter circuit. You do not need to redraw the power supply from part (a).

Part C:

Perform frequency response analysis for the amplifier and filter you designed in part (b) to calculate the gain in dB and phase in degrees when the microphone sends a signal at 100 Hz, 1k Hz and 10 kHz.

Part D:

Plot the response calculated in part (c) in a Bode plot.

Answer 1

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