Questions and Answers
In a voltage follower, the voltage gain is greater than 1.
False
What is the closed-loop voltage gain formula for a non-inverting amplifier?
What is the closed-loop voltage gain (Acl) if R1 = 100 kΩ and R2 = 4.7 kΩ?
22.28
In non-inverting amplifiers with negative feedback, _____ is the feedback factor.
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Match the following terms with their descriptions:
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What is the primary purpose of negative feedback in operational amplifiers?
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Negative feedback increases the output voltage of an operational amplifier.
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What is the effect of negative feedback on op-amp impedances?
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The formula for closed-loop gain (Acl) of an op-amp with negative feedback is given by: $Acl = \frac{V_{out}}{V_{in}}$ or simply expressed as $\frac{R_f}{R_i}$ where Rf is the feedback resistor and Ri is the __________.
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Match the following concepts related to operational amplifiers with their definitions:
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Study Notes
Introduction to Operational Amplifiers
- Operational amplifiers (op-amps) are high-gain voltage amplifiers with differential inputs and typically a single-ended output.
- Characterized by high open-loop gain (Aol), often around 100,000 or more.
Op-Amp Input Modes and Parameters
- Two main input configurations: inverting and non-inverting modes.
- Key parameters include input impedance, output impedance, voltage gain, and bandwidth.
Negative Feedback
- Negative feedback involves returning a portion of the output voltage to the input to stabilize and control the amplifier.
- It reduces distortion and improves linearity, allowing the op-amp to function as a linear amplifier.
Effects of Negative Feedback on Op-Amp Impedances
- Negative feedback significantly impacts op-amp input and output impedances, improving input impedance and reducing output impedance.
Open-Loop Frequency and Phase Responses
- Open-loop frequency response reveals how the gain of an op-amp changes with frequency without feedback.
- The phase response indicates the phase shift introduced by the op-amp at different frequencies.
Closed-Loop Frequency Response
- Closed-loop frequency response pertains to how gain behaves under feedback conditions.
- It allows defining a reliable performance range for the op-amp, crucial for stability and design considerations.
Non-Inverting Amplifier Configuration
- Closed-loop gain (Acl) can be calculated, where Acl = 1 + (R1/R2) for a non-inverting amplifier.
- High input impedance and low output impedance, facilitating voltage following applications.
Inverting Amplifier Configuration
- The closed-loop gain formula for an inverting amplifier is Acl = - (Rf/Rin).
- Demonstrates that the gain is independent of the op-amp’s internal gain, reinforcing the stability through negative feedback.
Voltage Follower Configuration
- Acts as an ideal buffer with a gain of 1, providing very high input impedance and low output impedance.
Example Calculations
- Non-inverting amplifier example: Given R1 = 100kΩ and R2 = 4.7kΩ, the closed-loop gain Acl = 22.28.
- Inverting amplifier requirement: To achieve a closed-loop gain of -100, Rf should be 220kΩ when Rin is 2.2kΩ.
Summary of Applications
- Negative feedback configurations are fundamental in amplifiers used in audio, control systems, and signal processing to ensure accurate and stable performance.
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Description
This quiz covers key concepts related to operational amplifiers, including their characteristics, input modes, and the effects of negative feedback. Participants will explore fundamental principles and applications of op-amps, and how they can be utilized in various electronic circuits.
