Input Resistance with Feedback of Feedback Transresistance Amplifier (Shunt-Shunt) Calculator

Formula Used:

\[ R_{inf} = \frac{R_{in}}{1 + A \cdot \beta} \]

Input Resistance with Feedback (Rinf):

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1. What is Input Resistance with Feedback?

The input resistance with feedback of a feedback amplifier is equal to the source impedance for which loop gain would drop to unity. It is a key parameter in analyzing the performance of feedback amplifier circuits, particularly in shunt-shunt configurations.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ R_{inf} = \frac{R_{in}}{1 + A \cdot \beta} \]

Where:

\( R_{inf} \) — Input Resistance with Feedback (Ohm)
\( R_{in} \) — Input Resistance (Ohm)
\( A \) — Open Loop Gain of an Operational Amplifier
\( \beta \) — Feedback Factor

Explanation: This formula demonstrates how feedback reduces the input resistance of an amplifier circuit by a factor of (1 + A·β), which is a fundamental property of negative feedback systems.

3. Importance of Input Resistance with Feedback

Details: Understanding input resistance with feedback is crucial for designing amplifier circuits with specific impedance matching requirements, ensuring proper signal transfer, and analyzing circuit stability in feedback configurations.

4. Using the Calculator

Tips: Enter input resistance in Ohms, open loop gain, and feedback factor. All values must be valid positive numbers (Rin > 0, β > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of input resistance with feedback?
A: It determines how the amplifier loads the source and affects signal transfer efficiency in the circuit.

Q2: How does feedback affect input resistance?
A: Negative feedback typically reduces the input resistance in shunt-shunt configurations, improving circuit performance.

Q3: What are typical values for these parameters?
A: Input resistance can range from hundreds to millions of Ohms, open loop gain is typically very high (10^5-10^6), and feedback factor is usually less than 1.

Q4: When is this calculation most important?
A: This calculation is critical when designing precision amplifiers, instrumentation circuits, and systems requiring specific impedance characteristics.

Q5: Are there limitations to this formula?
A: This formula assumes ideal amplifier characteristics and may need adjustment for real-world components with non-ideal behavior.