Low Power, 18 MHz Variable Gain Amplifier
The AD8338 is a variable gain amplifier (VGA) for applications that require a fully differential signal path, low power, low noise, and a well-defined gain over frequency. Although the inputs are differential, the device can also be driven with a single-ended source if required.
The basic gain function is linear-in-dB and is controlled by the voltage applied to Pin GAIN. The nominal gain range spans from 0 dB to 80 dB for control voltages between 0.1 V to 1.1 V with a slope of 12.5 mV/dB. The nominal gain range can be shifted up or down via direct access to Pin INPD and Pin INMD, the current inputs of the VGA. For example, driving the INPD and INMD pins with 50 Ω resistors shifts the gain range up by 20 dB, that is, 20 dB to 100 dB, and lowers the input referred noise of the device to 1.5 nV/√Hz. Additionally, the gain slope can be inverted via logic Pin MODE.
The AD8338 includes additional circuit blocks to enable input offset correction and automatic gain control (AGC). DC offset voltages are removed by the offset correction circuit, which behaves like a high-pass filter whose corner is set with an external capacitor. The AGC function varies the gain of the AD8338 to maintain a constant rms output voltage. An externally applied voltage to Pin VAGC with respect to the voltage at Pin VREF sets the output rms amplitude. A capacitor from Pin DETO to ground sets the response time of the AGC circuit.
The AD8338 offers additional versatility by providing access to the internal summing nodes of the VGA core and the output amplifiers. With the addition of a few external passive components, users can customize the gain, bandwidth, input impedance, and noise profile of the device to fit their application.
The AD8338 uses a single-supply voltage of 3.0 V to 5.0 V and is very power efficient, consuming as little as 3 mA quiescent current at mid gain. The AD8338 is available in a 3 mm × 3 mm, RoHS-compliant, 16-lead LFCSP and is specified over the industrial temperature range of −40°C to +85°C.
- Front end for inductive telemetry systems
- Ultrasonic signal receivers
- Signal compression for driving an ADC
- AGC amplifiers
This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
The AD8338 data sheet covers the details of the device’s operation. Using this data sheet for reference will help the designer in their end application. The data sheet is helpful for understanding the operation of the AD8338 evaluation board, especially during the initial configuration and when powering up for the first time.
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
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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.