The electrical signal is amplified, filtered and converted to digital format by the analog front end. This occurs directly after the signals are converted from acoustic to electrical signals at the probe. As can be seen in the block diagram on the right side of this slide, the analog front end consists of a low-noise amplifier, the voltage controlled attenuator, the programmable gain amplifier, a low pass filter and the analog to digital converter. The signals coming from the transducer that are reflected immediately are very strong. These reflections come from the top of the surface and are referred to as near field. Reflections that occur longer after the transmit pulse has happened are very weak, being reflected from deep in the body. These are called the far fields. The LNA function is to provide low noise amplification when scanning the far field tissues. Good sensitivity in the LNA is needed to detect very low level signals. The VCA and PGA are sometimes called the time gain control block. This TGC improves the system’s dynamic range and determines how well the system will detect the far field tissue without compromising the near field performance. The TGC block allows the gain to increase with time to compensate for the increased attenuation of the signal as it passes through the body. After the TGC block comes the filter, which improves the signal-to-noise ratio. The final stage is the ADC where the signal is converted to digital format. The SNR and the power consumption of the ADC are the key characteristics that require consideration when choosing components. The performance of the AFE significantly drives the ultrasound system’s size, weight, battery life, and image quality.