The variable dynamic range (VDR) provides waveband, high resolution, and fast sample rate to digital predistortion (DPD) observation receivers. VDR can also achieve full the bandwidth and dynamic range of the analog-to-digital converter, an immediate response to peak conditions, and synchronization without external hardware which reduces the signal routing and system complexity. This application note discusses the use of VDR in detail, as well as its traditional techniques, and specific application examples.