The AD8309 is a 100 dB dynamic range, single supply, high gain, low noise, low distortion, low power multistage log-limiter amplifier, which supports frequency and phase modulation applications. It has fixed phase, wide bandwidth, low input impedance and high output current.
The AD8309 is a fully differential logarithmic amplifier with limiter, covering 5 MHz to 500 MHz and offering a 100 dB dynamic range (‑78 dBm to +22 dBm). It operates from a single supply of 2.7 V to 6.5 V, draws under 50 mW at 3 V, and provides a stable RSSI output with a 20 mV/dB slope.
The handbook includes a functional block diagram, pin configuration, absolute‑maximum ratings, ordering guide, typical performance graphs, and a theory‑of‑operation section that explains the cascade of six gain stages and the limiter design.
| Usable Frequency Range | 5 MHz – 500 MHz |
|---|---|
| Dynamic Range | 100 dB (‑78 dBm to +22 dBm) |
| Supply Voltage | 2.7 V – 6.5 V |
| Quiescent Current (Zero‑Signal) | 13 mA – 20 mA |
| RSSI Slope | 20 mV/dB |
| Input Resistance (Differential) | 800 Ω – 1200 Ω |
| Input Capacitance (Differential) | 2.5 pF |
The AD8309 operates from 5 MHz up to 500 MHz.
It can be powered from a single supply between 2.7 V and 6.5 V.
The RSSI output has a slope of 20 mV per dB.
It provides a 100 dB dynamic range, from –78 dBm to +22 dBm.