Amplifying signals using transistors and operational amplifiers
An amplifier increases the amplitude of a signal. It takes a small input signal and produces a larger output signal with the same shape.
Voltage Gain (A_v) = V_out / V_in
Gain in dB = 20 × log₁₀(A_v)
Output is inverted (180° phase shift) and amplified.
Gain = -R_f / R_in
Output is in phase with input and amplified.
Gain = 1 + (R_f / R_in)
Unity gain (1x), high input impedance, low output impedance.
Gain = 1 (0 dB)
High voltage gain, phase inversion.
Gain ≈ -R_c / R_e
Unity voltage gain, high current gain (emitter follower).
Gain ≈ 1
High voltage gain, no phase inversion, low input impedance.
Gain ≈ R_c / (r_e + R_e)