Question

A. Design a low-pass filter (op-amp based cascade design) that meets the following (30) requirements: 1. Cutoff frequency: 3.4 KHz Passband gain: 20 dB 2. 3. Stopband gain: -40 dB/decade 4. All resistors must be 1.0 kS2 or higher. You have completed the design and implementation of the LP filter and are ready to deliver the filter for production. However, you are informed that the customer made a mistake and actually needed a stopband gain of -60 dB/decade (not-40 dB/decade that you have used in your design). Which of the following options would you choose (one only)? Briefly explain the justification of your choice. B. 1. Go back to the drawing board and redesign the filter based on the new specifications. Delivery of the product will be delayed but the customer is responsible for the delay and should be charged for extra work as well. 2. Improvise a quick change/modification in your current design/implementation to meet the new specifications and still be able to deliver the product on-time (clearly explain the change/modification you would make). Your vacation is starting day after tomorrow. The customer made a mistake-not your problem, you have done your job. The customer should be given a neyw delivery date and a new invoice with added charges for the redesign. This o should go back in the regular que for redesign. 3. rder

Answer 1

Hello,
          Please find the answer to A attached as under. Please give a thumbs up rating if you find the answer useful! Have a rocking day ahead!

For a cut-off frequency of 3.4KHz, we have 1/(2*pi*R*C) = 3.4K. If R = 1K, then C = 46.8nF.

Since the change of gain is +20 to -40, this is -60dB decrease in gain after the cut off frequency. This indicates that a 3rd order filter in necessary.

Moreover, a passband gain of 20dB means a gain of 10.

Heres the filter attached:

Traditional Passive Lou Pass RC filter Active Op-amp and Feed back Resistor RESISTOR RESISTOR RESISTOR R3 Vout at Higher Amplitude and Low frequency Vin Active Low Pass Filter R = 1K and C = 46.8nF R3 = 9K and R2 = 1K

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