Amplifier suitable for use in a radiotelephone

#Generally, the present invention relates to amplifiers and more specifically to power amplifiers using transistors such as (metal oxide semiconductor field effect transistor) MOSFET transistors in a current mirror configuration.

#In the past, power amplifiers for radio communication devices, such as radiotelephones, have used bipolar transistors. The simplest and most cost effective approach for building the amplifier would be to mount the bipolar transistor die in an industry standard plastic surface mountable package, and soldering the package to a circuit board.

#A problem arose which made it impractical to use standard surface mount packaging in many power amplifier applications because bipolar transistors have an output signal and heat sink coming out of one side of the bipolar transistor die, and input signals and RF grounds coming out of the other side of the transistor die. The requirements of providing a low loss electrical path for the output signal and a thermally conductive path for heat dissipation on one side of the die, and low loss electrical paths for the input signal and electrically conductive paths for the RF grounds from the other side of the die necessitated the use of onboard die attachment process and a wirebond process to couple the transistors to a circuit board.

#FIG. 1 is an illustration in block diagram form of a radiotelephone communication system which may employ the current invention.

#FIG. 2 is an illustration in block diagram form of a transmitter in accordance with the present invention.

#FIG. 3 is a detailed illustration of a power amplifier in accordance with the present invention.

#FIG. 1 is an illustration in block diagram form of a radiotelephone communication system. The radiotelephone communication system 100 includes a remote transceiver 101 which sends and receives radio frequency (RF) signals to and from radiotelephones within a fixed geographic area. The radiotelephone 103 is one such radiotelephone contained within the geographic area. The radiotelephone 103 includes an antenna 105, a receiver 107, the transmitter 109, a controller 111, and a user interface 113.

#Upon reception of RF signals, the radiotelephone 103 receives the RF signals through the antenna 105. The antenna 105 converts the received RF signals into electrical RF signals for use by the receiver 107. The receiver 107 demodulates the electrical RF signals and recovers the data transmitted on the RF signals and outputs the data to the controller 111. The controller 111 formats the data into a recognizable voice or information for use by the user interface 113. The user interface 113 communicates the received information or voice to a user. Typically, the user interface includes a display, a key pad, a speaker and a microphone.

#Upon transmission of radio frequency signals from the radiotelephone 103 to the remote transceiver 101, the user interface 113 transmits user input data to the controller 111. The controller 111 typically includes a microprocessor, memory, and a power amplifier control circuit. The controller 111 formats the information obtained from the user interface and transmits it to the transmitter 109 for conversion into RF modulated signals via the data line 115. Additionally, the controller 111 supplies the transmitter 109 with a control signal 117 having a voltage level. The voltage level of the control signal 117 determines the power of the RF signal output from the transmitter 109. In the preferred embodiment, the transmitter 109 contains a multi-stage power amplifier configuration. The voltage of the control signal 117 is determined by a control circuit contained within the controller 111. The control circuit utilizes the power output feedback signal 119 to determine the proper voltage of the control signal 117.