Integrating coupling circuit for coupling a modulator to a ceramic filter, useful with amplitude modulation receivers
AssigneeSGS-Thomson Microelectronics S.A.
InventorsLuigi Anzini, Rinaldo Graziadei, Giorgio Rossi
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Abstract
An integrated coupling circuit for coupling a modulator to a ceramic filter in amplitude modulation receivers, which modulator includes an output stage comprising a pair of differential cells parallel-connected to each other. The coupling circuit comprises a pair of transistors connected to each other through their respective bases and forming a bridge circuit with a diode and third transistor. Each transistor in the pair is connected in a cascode configuration and powered from a respective current mirror circuit connected to an output terminal of the modulator.
Claims2
A modulator circuit for an AM radio receiver, comprising:
- (a) a balanced modulator comprising a first differential cell having inputs for receiving an AM modulated RF signal and outputs, an output stage having two outputs and comprising second and third parallel-connected differential cells whose inputs are connected to the outputs of the first differential cell;
- (b) a coupling circuit for connecting the balanced modulator to a ceramic filter and comprisig a bridge circuit formed by fourth and fifth transistors, having respective bases, emitters and collectors and connected to each other through their respective bases, and a diode and a sixth transistor having a collector, first nd second circuit mirror circuits each connected between one output of the output stage and one of the fourth and fifth transistors of the bridge circuit;
- (c) and a ceramic filter having an input and an output, the ceramic filter input being connected to the bridge circuit, the modulator circuit output being taken from the ceramic filter output.
Dependencies are inferred from the claim text.