Digitally controlled wideband variable gain amplifier

摘要

A variable gain amplifier having a stacked configuration of cascode connected groups of NPN transistors is arranged in a compact schematic design. A differential radio frequency input signal is received at input nodes which is directed to a fine gain control circuit which conducts at least a portion of the received RF signal to a coarse gain control circuit that is downstream of the fine gain control circuit. The coarse gain control circuit steers current to an output node. Gain control circuits include transistor pairs. The base electrodes of each transistor pair receive inverse control signals which cause only one of the transistors in the transistor pair to conduct current. Collector electrodes of each first transistor of the pair is coupled to a downstream node in the VGA circuit, while collector electrodes of each second transistor of the pair is shunted to the voltage rail.

主权项

1. An integrated circuit implementing a variable gain amplifier (VGA) comprising:
a pair of input transistors, each input transistor in the pair configured to receive a differential RF input signal; a fine gain control circuit configured to receive the differential RF input signal from a collector electrode of one of the input transistors in the pair of input transistors, wherein said fine gain control circuit is configured to steer at least a portion of the RF input signal to a downstream processing stage of the VGA; a coarse gain control circuit in the downstream processing stage configured to receive the at least a portion of the RF input signal from the fine gain control circuit, wherein the coarse gain control circuit steers at least a portion of the RF input signal provided by the fine gain control circuit to an output terminal of the VGA; wherein at least one of said fine gain control circuit and said coarse gain control circuit comprises a plurality of common base transistors.