Subelement D: Circuits— Topic 30: Op Amps
Question 3-30D5
Element 3 (GROL)Which of the following op-amp circuits is operated open-loop?
Explanation
An op-amp circuit is operated open-loop when there is no negative feedback path from the output back to the input. Without negative feedback, the op-amp's extremely high intrinsic gain causes the output to quickly saturate at one of the power supply rails (a logic high or low state) based on the small voltage difference between its inputs.
A **comparator (D)** is designed to operate precisely in this open-loop configuration. It takes two input voltages and outputs a digital high or low signal, indicating which input is greater. This saturating behavior is its intended function.
Conversely, non-inverting amplifiers (A), inverting amplifiers (B), and active filters (C) all use negative feedback. Negative feedback is crucial for these circuits to control their gain, stabilize their operation, and ensure the op-amp remains in its linear operating region, allowing them to amplify or filter analog signals accurately.
Related Questions
3-30D3 Gain of a closed-loop op-amp circuit is determined by?3-30D4 Where is the external feedback network connected to control the gain of a closed-loop op-amp circuit?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?3-31D1 What frequency synthesizer circuit uses a phase comparator, look-up table, digital-to-analog converter, and a low-pass antialias filter?3-31D2 A circuit that compares the output of a voltage-controlled oscillator (VCO) to a frequency standard and produces an error voltage that is then used to adjust the capacitance of a varactor diode used to control frequency in that same VCO is called what?