Abstract: A power amplifier clipping circuit prevents sudden output changes when clipped from excessive input voltage, and includes an input voltage divider, two bias transistors connected to a positive voltage source, a third bias transistor connected to the first bias transistor and a first differential amplifier, a first current source connected to the third bias transistor and a negative voltage source and the first differential amplifier, fourth and fifth bias transistors connected to a negative voltage source and a second differential amplifier, a sixth bias transistor connected to the fourth bias transistor and the second differential amplifier, a second current source connected to the sixth bias transistor and a positive voltage source, a first output voltage controller connected between the negative voltage source and an output with a serial input resistor, and a second output voltage controller connected between the positive voltage source and the output and power amplifier.

Abstract: An apparatus for detecting a pilot signal. A phase detector detects a phase difference between a filtered amplitude-modulated pilot signal and a frequency divided signal, and a low pass filter low-pass-filters the phase difference. A voltage-controlled oscillator outputs a clock signal having a frequency determined by an output signal of the low-pass filter and outputs the clock signal having the frequency determined by an oscillation control signal. A (1/N) frequency divider divides the switching signal and outputs the (1/N) divided signal as a frequency divided signal, and an envelope detector detects an envelope of the filtered amplitude-modulated pilot signal and outputs the detected envelope as the pilot signal. The frequency of the pilot signal has information used to discriminate a broadcasting state. Therefore, the manufacturing cost and the number of pins in an integrated circuit can both be reduced.