50 dB GSM PA Controller
The AD8315 is a complete low cost subsystem for the precise control of RF power amplifiers operating in the frequency range 0.1 GHz to 2.5 GHz and over a typical dynamic range of 50 dB. It is intended for use in cellular handsets and other battery-operated wireless devices. The log amp technique provides a much wider measurement range and better accuracy than controllers using diode detectors. In particular, its temperature stability is excellent over a specified range of -30°C to +85°C.
Its high sensitivity allows control at low signal levels, thus reducing the amount of power that needs to be coupled to the detector.
The AD8315 is available in MSOP and LFCSP packages and consumes 8.5 mA from a 2.7 V to 5.5 V supply. When powered down, the sleep current is 4 µA.
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At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
AD8315-EVAL is a fully populated, 4-layer, FR4-based evaluation board. For normal operation, it requires a 2.7V to 5V/15 mA power supply. The power supply should be connected to the vector pins leads labeled VPOS and GND. The RF input signal is applied to the edge-mounted SMA type RF connector (RFIN). The setpoint input signal is applied to the edge-mounted SMA type connector (VSET). The detector output signal is accessible via the edge-mounted SMA connector (VAPC ). The circuit board can accommodate configuration in controller mode and a quasi-measurement mode (via an op-amp feedback loop) depending on the status the jumpers (LK1, LK2).
Ask The Applications Engineer - 28 Logarithmic Amplifiers-Explained
(Analog Dialogue, Vol. 33, No. 3, March, 1999)