Overview
The AD8326AREZ is a high-output power, digitally controlled, variable gain amplifier designed by Analog Devices Inc. This component is optimized for coaxial line driving applications, particularly in data and telephony cable modems that adhere to the MCNS-DOCSIS upstream standard. The AD8326 features a low noise, fixed-gain buffer, a digitally controlled variable attenuator, and a low distortion high-power amplifier. It supports both differential and single-ended input signals and is designed to drive a 75 Ω load, such as coaxial cable.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Input Resistance (Differential) | 1600 | Ω | ||
| Input Resistance (Single-Ended) | 800 | Ω | ||
| Input Capacitance | 2 | pF | ||
| Gain Range | 52.5 | 53.5 | 54.5 | dB |
| Maximum Gain | 26.5 | 27.5 | 28.5 | dB |
| Minimum Gain | -27 | -26 | -25 | dB |
| Gain Scaling Factor | 0.7526 | dB/LSB | ||
| Bandwidth (–3 dB) | 100 | MHz | ||
| Output Noise Spectral Density (Max Gain, f = 10 MHz) | -28 | dBmV |
Key Features
- Digitally controlled variable gain over a 53.5 dB range with 0.75 dB/LSB resolution.
- Low noise, fixed-gain buffer and low distortion high-power amplifier.
- Supports both differential and single-ended input signals.
- Designed to drive a 75 Ω load, such as coaxial cable.
- Controlled through a serial peripheral interface (SPI) with three digital data lines (CLK, DATEN, and SDATA).
- Includes a vernier stage for fine-tune gain adjustment and a DAC for bulk attenuation.
- Utilizes negative feedback to implement a differential 75 Ω output impedance, eliminating the need for external matching resistors.
Applications
- Coaxial line driving in data and telephony cable modems.
- Compliance with MCNS-DOCSIS upstream standard.
- Other high-output power applications requiring precise gain control.
Q & A
- What is the primary function of the AD8326AREZ?
The AD8326AREZ is a high-output power, digitally controlled, variable gain amplifier optimized for coaxial line driving applications.
- What is the gain range of the AD8326AREZ?
The gain range is 53.5 dB with a resolution of 0.75 dB/LSB.
- How is the AD8326AREZ controlled?
It is controlled through a serial peripheral interface (SPI) with three digital data lines (CLK, DATEN, and SDATA).
- What type of input signals does the AD8326AREZ support?
The AD8326AREZ supports both differential and single-ended input signals.
- What is the output impedance of the AD8326AREZ?
The output impedance is a differential 75 Ω, implemented using negative feedback.
- What are the typical applications of the AD8326AREZ?
Typical applications include coaxial line driving in data and telephony cable modems, particularly those adhering to the MCNS-DOCSIS upstream standard.
- What is the bandwidth of the AD8326AREZ?
The bandwidth is 100 MHz (–3 dB).
- How does the AD8326AREZ achieve fine-tune gain adjustment?
The AD8326AREZ includes a vernier stage for fine-tune gain adjustment and a DAC for bulk attenuation.
- What is the input resistance of the AD8326AREZ for differential inputs?
The input resistance for differential inputs is 1600 Ω.
- What is the output noise spectral density of the AD8326AREZ at maximum gain and 10 MHz?
The output noise spectral density is –28 dBmV.
