This example shows how noise can be incorporated into an electrical simulation. The circuit models an amplifier with gain 100 and a high-frequency roll off frequency of 10MHz. The op-amp adds noise, and it is assumed that the datasheet specifies an equivalent voltage noise density of 20nV/Hz^0.5. This is implemented using the noise voltage source Vn. Optionally, the thermal noise generated by resistors R1 and R2 can also be included by selecting 'Enabled' for the blocks' noise mode. However, running this model with different combinations of noise sources shows that the main source of noise is the equivalent noise voltage.
Warning: The file containing block diagram 'ee_opamp_noise' is shadowed by a file of the same name higher on the MATLAB path. This can cause unexpected behavior. For more information see <a href="matlab:helpview([docroot '/toolbox/simulink/helptargets.map'], 'shadowing')">"Avoiding Problems with Shadowed Files"</a> in the Simulink documentation. The file containing the block diagram is: /mathworks/devel/bat/Bdoc19b/build/matlab/toolbox/physmod/elec/eedemos/ee_opamp_noise.slx. The file higher on the MATLAB path is: /mathworks/devel/bat/Bdoc19b/build/matlab/toolbox/physmod/elec/eedemos/html/ee_opamp_noise.m