Keysight (Agilent) 11909A Low Noise Amplifier, 9 kHz to 1 GHz

The Keysight (Agilent) 11909A is a low-noise amplifier that extends measurement system sensitivity across 9 kHz to 1 GHz by delivering 32 dB gain with minimal noise contribution. Designed for precision detection of weak signals, it operates with a noise figure of 1.8 dB typical (5 MHz to 500 MHz) and maintains gain flatness of ±0.5 dB across most of its operating range. The amplifier handles up to +10 dBm output at 1 dB compression point and accepts maximum linear input of ±24 mV, making it suitable for applications where signal fidelity and system noise performance directly impact measurement accuracy.

Technical Specifications

• Frequency range: 9 kHz to 1 GHz (–3 dB)


• Amplifier gain: 32 dB ± 1.5 dB @ 100 MHz


• Gain flatness: ±0.5 dB (25 kHz to 800 MHz) Noise Performance


• Noise figure: 1.8 dB typical, 2.5 dB maximum (5 MHz to 500 MHz)


• Noise figure: 2.5 dB typical (1 GHz) Power & Impedance


• Output power at 1 dB compression: +10 dBm


• Impedance: 50 ohms


• Input return loss: 8 dB


• Output return loss: 10 dB


• Reverse isolation: 35 dB Input Protection


• Maximum input for linear operation: ±24 mV


• Input damage level: ±2 V DC Environmental & Power


• Operating temperature: 0 °C to 55 °C


• Storage temperature: –25 °C to 75 °C


• Power supply: 100, 120, 220, or 240 V AC, 50/60 Hz, 20 VA Physical


• Dimensions: 91 mm (H) × 109 mm (W) × 183 mm (D)


• Weight: 3.3 lbs (1.5 kg)


• Connectors: Type N input/output

Key Features

• Low-noise design optimized for weak signal detection


• Stable gain across 9 kHz to 1 GHz bandwidth


• 50 ohm matched input and output


• Direct integration with spectrum analyzers and receiver systems

Typical Applications

• Enhancing receiver and spectrum analyzer sensitivity


• Close-field probe measurements for device emissions


• Radiated emissions testing with antenna-based systems

Compatibility & Integration The 11909A pairs with Keysight (Agilent) 11940A and 11941A close-field probes for low-level emission detection.