Product Features
Wide range of analog variable gain: -2.5 dB to 42.5 dB
3 dB cutoff frequency at 500 MHz
Gain and gain reduction modes
Linear decibel, scaled to 20 mV/ dB
Resistive grounded reference input
Nominal ZIN = 200 Ω
On-chip, square-law detector
Single power supply: 2.7 V to 5.5 V
Applications
Cellular base stations
Broadband access
Power amplifier control loop
Complete, linear IF AGC amplifier
High-speed data I/O
Overview
The AD8367 is linear in dB for gain control from low frequencies using a high performance 45 dB variable gain amplifier up to several hundred MHz range, flatness and gain response accuracy using ADI's X-AMP® architecture, a recent series of powerful proprietary concepts for variable gain applications, which far exceed what can be achieved using competing technologies.
The input is applied to a 9-stage, 200 Ω resistive ladder network. Each stage has a loss of 5 dB, giving a total attenuation of 45 dB. At maximum gain, the first tap is selected; at progressively lower gains, the tap moves smoothly and continuously toward higher attenuation values. Even at high frequencies, the attenuator is followed by a 42.5 dB fixed-gain feedback amplifier essentially an operational amplifier with 100 GHz, and a gain bandwidth product that is very linear. The output third-order intercept is 20 dB at 100 MHz (+27 dBm at 200 Ω), measured at an output level of 1 V PP with VS=5 V.

Gain curve at 32dB:

Gain curve at 20dB:

Gain curve at 10dB:

Small gain, broadband test: 500MHz bandwidth flatness

AD8367 maximum gain of 42dB is also achievable, the maximum gain of the analyzer small signal test: (input power: -40dB)

input signal:

Output signal: 10MHz -1.93dBm Gain value: 40dB

Output signal: 100MHz -1.93dBm Gain value: 40dB

Output signal: 150MHz -0.18dBm Gain value: 41dB

Output signal: 200MHz -0.18dBm Gain value: 40dB

Oscilloscope waveform test chart: