Publisher Summary The chapter defines noise as undesirable signals that are present in a circuit. The three types of noise in analog application are device noise, conducted noise, and radiated noise. Each type of noise has its own set of possible solutions. The first noise type is device noise. Device noise is the intrinsic noise of the devices in the circuit. Examples of device noise would be the thermal noise of a resistor or the shot noise of a transistor. Another type of device noise is the switching noise from a switched mode power supply or a switched capacitor converter. A second type of noise is radiated noise. Radiated noise originates with EMI sources, such as switches or motors. These sources couple radiated noise into a signal. Radiated noise can also transmit from trace to trace on one's printed circuit board (PCB). The third type of noise that affects the performance of analog devices is conductive noise. This type of noise already exists in the conductive paths of a circuit, such as the power lines or signal path. Conducted noise mixes with the desired electrical signal.