An Integrated 900MHz GSM Power Amplifier Control Circuit

An integrated power amplifier control system capable of meeting the GSM cellular telephone requirements is described. The integrated control ciruitry consists of a control up of an integrator, an RF detector, a selectable gain buffer, and also two comparators to monitor when the power amplifier is active or in saturation. A unique RF detection seheme which uses high speed Schottky diodes to rectify RF input signals has achievedd sensitivity levels of-18dBm at 900 MHz, 4db better than current discrete detector circuits. The new detector also has improved temperature stability and power supply rejection. A 5MHz, high gain (Av=110db) single supply amplifier which includes a new all NPN output stage with increased output dynamic range is shown. Finally, techniques for design of a precision comparator with low input offset voltage and less then 100ns propagation delay are described.