Low noise preamp simulation

noise.py

import numpy as np

noise_db = -80  # Noise added by each amplifier
gain_db = 60    # Closed loop gain

cycles = 2
resolution = 1000
length = np.pi * 2 * cycles
signal = np.sin(np.arange(0, length, length / resolution))
raw_noise = 10**(noise_db / 20)
raw_gain = 10**(gain_db / 20)

print("# opamps, simulated noise, theoretical noise")
for n_amps in range(1, 10):
    sum = np.zeros(len(signal))
    for _ in range(n_amps):
        sum += signal * raw_gain + np.random.normal(0, raw_noise, len(signal))

    # Total output through the voltage divider
    output = sum / n_amps

    # Subtract clean signal to get noise and calculate RMS noise
    noise_residual = output - signal * raw_gain
    noise_rms = np.sqrt(np.sum(noise_residual ** 2) / len(signal))
    print(n_amps, 20 * np.log10(noise_rms), noise_db - 20 * np.log10(np.sqrt(n_amps)))

Thank you for doing this much effort. I really appreciate it.