Element 3: General Radiotelephone

effective 6/25/2009

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3-D-030: Op Amps

3-30D1: What is the main advantage of using an op-amp audio filter over a passive LC audio filter?

Op-amps exhibit gain rather than insertion loss.

Op-amps are largely immune to vibration and temperature change.

Most LC filter manufacturers have retooled to make op-amp filters.

Op-amps are readily available in a wide variety of operational voltages and frequency ranges.



3-30D2: What are the characteristics of an inverting operational amplifier (op-amp) circuit?

It has input and output signals 180 degrees out of phase.

It has input and output signals in phase.

Input and output signals are 90 degrees out of phase.

Input impedance is low while the output impedance is high.



3-30D3: Gain of a closed-loop op-amp circuit is determined by?

The op-amp’s external feedback network.

The maximum operating frequency divided by the square root of the load impedance.

Supply voltage and slew rate.

The op-amp’s internal feedback network.



3-30D4: Where is the external feedback network connected to control the gain of a closed-loop op-amp circuit?

From output to the inverting input.

Between the differential inputs.

From output to the non-inverting input.

Between the output and the differential inputs.



3-30D5: Which of the following op-amp circuits is operated open-loop?

Comparator.

Non-inverting amp.

Inverting amp.

Active filter.



Figure 3D6

3-30D6: In the op-amp oscillator circuit shown in Figure 3D6, what would be the most noticeable effect if the capacitance of C were suddenly doubled?

Frequency would be lower.

Frequency would be higher.

There would be no change. The inputs are reversed, therefore the circuit cannot function.

None of the above.





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