While ultra-low noise is always a focus of audio engineers, the input-referred voltage noise of the amplifier is often the only parameter that is considered. If impedances from the source and feedback network are low, this is a reasonable consideration. However, for a power-conscious system, such as one powered by battery or USB, low impedances may not be an option. The circuit designer must consider the noise contribution of the input resistor to the total noise of the system in order to determine the optimal balance of noise and power.

TI has launched the next generation audio FDA, the OPA1637. This device utilizes TI’s novel analog bipolar process technology. Its use of super beta BJT devices can resolve the problems found in many audio applications.