Broadband noise is a noise that appears at higher frequency compared to 1/f noise. The broadband noise is usually flat and uniform over frequency as shown in Figure 8-40. The broadband noise is measured by high-pass filtering the output of the REF70 and measuring the result on a spectrum analyzer as shown in Figure 8-12. The DC component of the REF70 is removed by using a high-pass filter and then amplified. When measuring broadband noise, it is not necessary to have high gain in order to achieve maximum bandwidth.

For noise sensitive designs, a low-pass filter can be used to reduce broadband noise output noise levels by removing the high frequency components. When designing a low-pass filter special care must be taken to ensure the output impedance of the filter does not degrade ac performance. This can occur in RC low-pass filters where a large series resistance can impact the load transients due to output current fluctuations.