The AD8330 is a wideband variable gain amplifier for applications requires a fully differential signal path, low noise, well-defined gain and moderately low distortion, from dc to 150MHz. The input pins can also be driven from a single-ended source. The peak differential input is ±2V, allows sine wave operation at 1Vrms with generous headroom. The output pins can drive single-sided loads essentially rail-to-rail. The differential output resistance is 150?. The output swing is a linear function of the voltage applied to the VMAG pin that internally defaults to 0.5V, providing a peak output of ±2V. This can be raised to 10Vp-p, limited by the supply voltage.

The basic gain function is linear-in-dB, controlled by the voltage applied to Pin VDBS. The gain ranges from 0 dB to 50dB for control voltages between 0V and 1.5V a slope of 30mV/dB. The gain linearity is typically within ±0.1dB. By changing the logic level on Pin MODE, the gain decreases over the same range, with an opposite slope. A second gain control port is provided at the VMAG pin and allows the user to vary the numeric gain from a factor of 0.03 to 10. All the parameters of the AD8330 have low sensitivities to temperature and supply voltages.

Using VMAG, the basic 0dB to 50dB range can be repositioned to any value from 20dB higher (that is, 20dB to 70dB) to at least 30dB lower (that is, -30dB to +20dB) to suit the application, thereby providing an unprecedented gain range of over 100dB. A unique aspect of the AD8330 is that its bandwidth and pulse response are essentially constant for all gains, over both the basic 50dB linear-in-dB range, but also when using the linear-in-magnitude function. The exceptional stability of the HF response over the gain range is of particular value in those VGA applications where it is essential to maintain accurate gain law-conformance at high frequencies.