Overview
The AD8331ARQ, produced by Analog Devices Inc., is a single-channel, ultralow noise, linear-in-dB variable gain amplifier (VGA). This device is optimized for ultrasound systems but can also be used as a low noise variable gain element at frequencies up to 120 MHz. The AD8331 includes an ultralow noise preamplifier (LNA), an X-AMP® VGA with a 48 dB gain range, and a selectable gain postamplifier with adjustable output limiting. The LNA has a gain of 19 dB with a single-ended input and differential outputs, and the input impedance can be adjusted using a single resistor to match the signal source without compromising noise performance.
Key Specifications
| Parameter | Conditions | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Gain Range (LO gain) | -4.5 dB | +43.5 dB | |||
| Gain Range (HI gain) | +7.5 dB | +55.5 dB | |||
| Input Voltage Noise | RS = 0 Ω, HI or LO gain, RIZ = ∞, f = 5 MHz | 0.82 nV/√Hz | |||
| Input Resistance | RFB = ∞ | 6 kΩ | |||
| Input Capacitance | 13 pF | ||||
| Output Impedance (Single-Ended) | 50 Ω | ||||
| -3 dB Small Signal Bandwidth | VOUT = 0.2 V p-p | 120 MHz | |||
| -3 dB Large Signal Bandwidth | VOUT = 2 V p-p | 110 MHz | |||
| Slew Rate (LO gain) | 300 V/µs | ||||
| Slew Rate (HI gain) | 1200 V/µs | ||||
| Power Consumption | 125 mW/channel | ||||
| Operating Temperature Range | -40°C | +85°C |
Key Features
- Ultralow noise preamplifier (LNA) with 19 dB gain and single-ended input to differential output.
- X-AMP® VGA with 48 dB of gain range.
- Selectable gain postamplifier with adjustable output limiting.
- Active input impedance matching to optimize noise performance.
- Low output-referred noise: 48 nV/√Hz typical.
- Optimized for 10-bit/12-bit ADCs.
- Single 5 V supply operation.
- Available in a 20-lead QSOP package.
- Excellent bandwidth uniformity across the entire gain range.
- Precise linear-in-dB scaling of 50 dB/V for control voltages between 40 mV and 1 V.
- Factory trim ensures excellent part-to-part and channel-to-channel gain matching.
Applications
- Ultrasound and sonar time-gain controls.
- High performance automatic gain control (AGC) systems.
- I/Q signal processing.
- High speed, dual ADC drivers.
Q & A
- What is the gain range of the AD8331 in LO and HI gain modes?
The gain range is -4.5 dB to +43.5 dB in LO gain mode and +7.5 dB to +55.5 dB in HI gain mode.
- What is the typical output-referred noise of the AD8331?
The typical output-referred noise is 48 nV/√Hz.
- What is the bandwidth of the AD8331?
The -3 dB small signal bandwidth is 120 MHz, and the -3 dB large signal bandwidth is 110 MHz.
- How is the input impedance of the AD8331 adjusted?
The input impedance can be adjusted using a single resistor to match the signal source without compromising noise performance.
- What is the power consumption of the AD8331 per channel?
The power consumption is 125 mW per channel.
- What are the typical slew rates for the AD8331 in LO and HI gain modes?
The slew rates are 300 V/µs in LO gain mode and 1200 V/µs in HI gain mode.[
- What is the operating temperature range of the AD8331?
The operating temperature range is -40°C to +85°C.
- What package types are available for the AD8331?
The AD8331 is available in a 20-lead QSOP package.[
- What are some of the key applications of the AD8331?
Key applications include ultrasound and sonar time-gain controls, high performance AGC systems, I/Q signal processing, and high speed dual ADC drivers.[
- How does the AD8331 optimize noise performance?
The AD8331 optimizes noise performance through active input impedance matching.[
