Practice Effect On Input Resistance (zinf) (5.3.3) - Feedback Amplifiers and Stability
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Effect on Input Resistance (Zinf)

Practice - Effect on Input Resistance (Zinf)

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Practice Questions

Test your understanding with targeted questions

Question 1 Easy

What is input resistance (Zinf)?

💡 Hint: Think about how input voltage and current relate.

Question 2 Easy

How does negative feedback affect Zinf in series configurations?

💡 Hint: Consider the effect of opposition to the input current.

4 more questions available

Interactive Quizzes

Quick quizzes to reinforce your learning

Question 1

What is the formula for calculating Zinf in series feedback configurations?

Zinf = Zin (1 + AβF)
Zinf = Zin / (1 + AβF)
Zinf = 1 + AβF Zin

💡 Hint: Think about how current flows with feedback.

Question 2

True or False: Shunt feedback increases the input resistance of an amplifier.

True
False

💡 Hint: Consider how input currents behave in shunt feedback.

1 more question available

Challenge Problems

Push your limits with advanced challenges

Challenge 1 Hard

Consider an amplifier with an open-loop input impedance of 1 MΩ and a feedback factor of 0.005 in a series connection. Calculate the input resistance Zinf. Explain how the result would change if shunt feedback was applied instead.

💡 Hint: Calculate first, then use the feedback topology to explain the difference.

Challenge 2 Hard

You have a voltage amplifier designed for a sensor with high output impedance. Define appropriate feedback topology and justify your choice based on Zinf calculations. What would happen if shunt topology is incorrectly applied?

💡 Hint: Think about how the feedback informs the interface with the sensor.

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