July 2024 StudentZone Quiz Solution

SHusted

on Jun 26, 2024

Question:

Considering the circuit in Figure 1, change the gain of the amplifier by replacing the values of R3 and R4. What do you observe with the frequency response?

Answer:

As mentioned in the lab activity, the R3 and R4 resistors modify the gain of the amplifier, following the equation:

Therefore, increasing the value of R3 will result in a higher voltage at the output of the Sallen-Key second-order low-pass filter circuit, while increasing the value of R4 will result in a smaller voltage at the output of the circuit.

See the article: www.analog.com/.../studentzone-july-2024.html

RobertAlladex
on Oct 3, 2024 1:35 PM
Because the cutoff frequency (fc) is dependent on R1, R2, C1, C2

Changing the values of R3 and R4 will only shift the Bode plot (magnitude part of freq response) up or down. Also there are limitations on how much gain can achieved by varying R3 and R4.The amplifier gain A can be considered open loop gain

If you plot the root-locus of the system, you'll realize that if you keep on increasing A beyond a certain threshold, the system may oscillate. Analytically, the max open loop gain A can be calculated using Routh-Hurwitz criteria
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