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October 2021 StudentZone Quiz Solution

Question 1:

For the circuit in Figure 1 what is the gain from the input source, W1, to the output seen at RL? Which components set this gain?

Answer 1:

 The gain of the amplifier circuit in Figure 1 is set by the R1 and R2 resistors. The gain of the circuit can be obtained similar to the inverting operational amplifier which has the gain defined by the following formula:

Therefore, following the values used in the circuit, we obtain a gain value around -4.7.

Question 2:

Change the value of compensation capacitor C3. How does raising and lowering the value of C3 affect the frequency response?

Answer 2:

The easiest way to answer this question is to build the circuit using a simulation tool like LTspice and run an AC analysis type simulation that has the start frequency around 10Hz and stop frequency around 10MHz.

A circuit example is presented in the figure below.

By lowering the value of C3, we will notice in the frequency response plot of the circuit that the frequency range in which the amplifier operates will increase, while raising the value of the capacitor will result in a narrower frequency operation range.