Dual, Low Noise, Single-Supply Variable Gain Amplifier
The high performance linear-in-dB response of the AD605 is achieved with the differential input, single-supply, exponential amplifier (DSX-AMP) architecture. Each of the DSX-AMPs comprises a variable attenuator of 0 dB to −48.4 dB followed by a high speed, fixed-gain amplifier. The attenuator is based on a 7-stage R-1.5R ladder network. The attenuation between tap points is 6.908 dB, and 48.360 dB for the entire ladder network. The DSX-AMP architecture results in 1.8 nV/√Hz input noise spectral density and accepts a ±2.0 V input signal when VOCM is biased at VP/2.
Each independent channel of the AD605 provides a gain range of 48 dB that can be optimized for the application. Gain ranges between −14 dB to +34 dB and 0 dB to +48 dB can be selected by a single resistor between Pin FBK and Pin OUT. The lower and upper gain ranges are determined by shorting Pin FBK to Pin OUT or leaving Pin FBK unconnected, respectively. The two channels of the AD605 can be cascaded to provide 96 dB of very accurate gain range in a monolithic package.
The gain control interface provides an input resistance of approximately 2 MΩ and scale factors from 20 dB/V to 30 dB/V for a VREF input voltage of 2.5 V to 1.67 V, respectively. Note that scale factors up to 40 dB/V are achievable with reduced accuracy for scales above 30 dB/V. The gain scales linearly in dB with control voltages (VGN) of 0.4 V to 2.4 V for the 20 dB/V scale and 0.20 V to 1.20 V for the 40 dB/V scale. When VGN is <50 mV, the amplifier is powered down to draw 1.9 mA. Under normal operation, the quiescent supply current of each amplifier channel is only 18 mA.
The AD605 is available in a 16-lead PDIP and a 16-lead SOIC_N package and is guaranteed for operation over the −40°C to +85°C temperature range.
Data Sheet, Rev. E, 5/07
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
The AD605 evaluation board is a factory-designed, surface-mount assembly fully tested and ready for service. The AD605-EVALZ. This board has multiple inputs, test points, and jumpers provide circuit configurations that support any of the operating options of the device. See the AD605 data sheet available on line for schematics and further details.
Product Selection Guide
Variable Gain Amplifier Selection Table
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The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.