def _input_V_calcs(input_V, A2, rho_amp):
    """Get the effective preamp input noise current (ENI) and the output
    noise voltage from the noise voltage at the preamp input.

    :return: output voltage, effective input current (ENI)
    """
    output_V = A2 * input_V
    eni = input_V / rho_amp

    return output_V, eni