Apparatus and methods for overdrive protection of radio frequency amplifiers

摘要

Provided herein are apparatus and methods for overdrive protection of radio frequency (RF) amplifiers. In certain configurations, an RF amplifier includes a plurality of amplification stages and an overdrive detection circuit. The overdrive detection circuit determines whether or not the RF amplifier is in an overdrive condition based on a current of an input amplification stage. Additionally, when the overdrive detection circuit detects an overdrive condition, the overdrive detection circuit controls an impedance of one or more feedback circuits of one or more amplification stages subsequent to the input amplification stage in a signal path of the RF amplifier to reduce the RF amplifier's gain. The overdrive protection schemes herein can be used to limit large current and voltage swing conditions manifesting within amplification transistors of the RF amplifier.

主权项

1. A radio frequency amplification system comprising:
a plurality of radio frequency amplification stages configured to amplify an input signal to generate an output signal, the plurality of radio frequency amplification stages including a first amplification stage and a second amplification stage that is subsequent to the first amplification stage in a signal path, the first amplification stage including a first stage bipolar transistor, and the second amplification stage including a second stage bipolar transistor and a base-to-collector feedback circuit electrically connected between a base and a collector of the second stage bipolar transistor; and an overdrive detection circuit configured to sense a collector current of the first stage bipolar transistor to detect when an overdrive condition is present, and to decrease an impedance of the base-to-collector feedback circuit in response to detection of the overdrive condition such that a gain of the second stage bipolar transistor is reduced.