Input Resistance With Feedback Current Amplifier Calculator

Input Resistance With Feedback Formula:

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

Input Resistance With Feedback (R_inf):

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1. What is Input Resistance With Feedback?

Input resistance with feedback of a feedback amplifier is equal to the source impedance for which loop gain would drop to unity. It represents the effective input resistance when negative feedback is applied to an amplifier circuit.

2. How Does the Calculator Work?

The calculator uses the Input Resistance With Feedback formula:

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

Where:

\( R_{inf} \) — Input resistance with feedback (Ohm)
\( R_{in} \) — Input resistance without feedback (Ohm)
\( A\beta \) — Loop gain (dimensionless)

Explanation: The formula shows how negative feedback reduces the input resistance of an amplifier. The higher the loop gain, the more the input resistance is reduced.

3. Importance of Input Resistance Calculation

Details: Calculating input resistance with feedback is crucial for designing amplifier circuits, ensuring proper impedance matching, and predicting circuit behavior in feedback configurations.

4. Using the Calculator

Tips: Enter input resistance in Ohms and loop gain value. Both values must be valid (input resistance > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is loop gain in amplifier circuits?
A: Loop gain is the product of the amplifier gain and the feedback factor. It determines how much negative feedback is applied to the circuit.

Q2: How does negative feedback affect input resistance?
A: Negative feedback typically reduces the input resistance of current amplifiers, making the circuit less sensitive to input signal variations.

Q3: What are typical values for input resistance?
A: Input resistance values vary widely depending on the amplifier type, ranging from a few ohms to several megaohms.

Q4: When is this calculation most important?
A: This calculation is particularly important when designing feedback amplifier circuits for specific impedance requirements or when analyzing circuit stability.

Q5: Can this formula be used for all amplifier types?
A: This formula specifically applies to current amplifiers with negative feedback. Different formulas apply for voltage amplifiers and other amplifier configurations.