Noninverting Amplifier, the op-amp parameters are given as follows:
A = 200,000, Zin = 1MΩ and Zout=100Ω.
Calculate the amplifier input impedance (with negative feedback).
rf =47kΩ
ri = 1.0kΩ
The amplifier input impedance with negative feedback can be calculated using the formula:
Zin(f) = Zin / (1 + Aβ)
where β is the feedback fraction, which is equal to rf / (rf + ri).
Substituting the given values, we get:
β = rf / (rf + ri) = 47kΩ / (47kΩ + 1.0kΩ) = 0.979
Zin(f) = 1MΩ / (1 + 200,000 * 0.979) = 5.11 kΩ
Therefore, the amplifier input impedance with negative feedback is 5.11 kΩ.
To calculate the amplifier input impedance, we can use the formula:
Zin = ri || (1 + A) * (rf)
Where || represents the parallel combination.
Given values:
A = 200,000
Zin = 1MΩ
rf = 47kΩ
ri = 1.0kΩ
Substituting the values into the formula, we get:
Zin = 1.0kΩ || (1 + 200,000) * (47kΩ)
= 1.0kΩ || 200,001 * 47kΩ
= 1.0kΩ || 9,400,047kΩ
= 1.0kΩ || 9,400,047kΩ / 1,000
= 1.0kΩ || 9,400.047kΩ
≈ 999.999Ω
Therefore, the amplifier input impedance (with negative feedback) is approximately 999.999Ω.