AD8368,pdf datasheet (Variable

The AD8368 is a variable gain amplifier (VGA) with analog linear-in-dB gain control that can be used from low frequencies to 800 MHz. Its excellent gain range, conformance, and flatness are attributed to the Analog Devices, Inc., X-AMP® architecture, an innovative technique for implementing high performance variable gain control.
The gain range of −12 dB to +22 dB is scaled accurately to 37.5 dB/V with excellent conformance error. The AD8368 has a 3 dB bandwidth of 800 MHz that is nominally independent of gain setting. At 140 MHz, the OIP3 is 33 dBm at maximum gain. The output noise floor is −143 dBm/Hz, which corresponds to a 9.5 dB noise figure at maximum gain. The single-ended input and output impedances are nominally 50 Ω.
The gain of the AD8368 can be configured to be an increasing or decreasing function of the gain control voltage depending on whether the MODE pin is pulled to the positive supply or to ground, respectively. When MODE is pulled high, the AD8368 operates as a typical VGA with increasing gain.