Mitel Semiconductor Limited

Viatcheslav Igor Souetinov

Peter G Laws

An amplifier circuit arrangement comprises first and second long-tailed pairs of transistors each including an inductor to provide a constant current source for their respective transistor pair. Each of the transistors of the pairs is provided with a bias current on its base electrode. A differential input signal is applied between the base electrode of one transistor, via a dc blocking capacitor and an input terminal, and the base electrode of another transistor, via a dc blocking capacitor and an another input terminal. The collector electrodes of two of the transistors are connected together and to an output terminal. The collector electrodes of the other two transistors similarly are connected together and to the other output terminal. A differential output signal is provided between the output terminals. This connection of the collectors of the transistors, which can be described as parallel connection, provides summation of the differential signals provided by the transistor pairs.

Differential amplifier with two long-tailed pairs of transistors

An image reject mixer for a radio receiver comprises transconductors,and,, mixer stages,and,and a phase shift and combiner circuit,The transconductors,and,provide differential output current signals to their respective mixer stage,and,. Capacitors,and,are connected between equivalent outputs of the transconductors,and,respectively. The capacitors,and,have the effect of correlating the output noise of the transconductors,and,and correlating the noise generated by the mixer stage transistors which is leaked to the inputs of the mixer stages,and,, the image frequency components of which noise are thereby cancelled by the operation of the mixer stages,and,and the phase shift and combiner circuit,The capacitors,and,also compensate the second harmonic of the local oscillators which leak through to the inputs of the mixer stages,and,Overall, gain, noise figure and linearity can all be improved without an increase in current consumption.

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Swindon, United Kingdom

Viatcheslav Igor Souetinov