Low noise amplifier circuit

Abstract

An amplifier for converting a single-ended input signal to a differential output signal. The amplifier comprises a first transistor, a second transistor, a third transistor and a fourth transistor. The first transistor, configured in common-source or common-emitter mode, receives the single-ended input signal and generates a first part of the differential output signal. The second transistor, also configured in common-source or common-emitter mode, generates a second part of the differential output signal. The third and fourth transistors are capacitively cross-coupled. The amplifier further comprises inductive degeneration such that a source or emitter of the first transistor is connected to a first inductor and a source or emitter of the second transistor is connected to a second inductor.

1 . A low noise amplifier for converting a single-ended input signal to a differential output signal, the amplifier comprising:
 a first transistor, configured in common-source mode, to receive the single-ended input signal and generate a first part of the differential output signal;   a second transistor, configured in common-source mode, to generate a second part of the differential output signal; and   a third transistor and a fourth transistor, and wherein the third transistor and forth transistor are cross-coupled and connected to the first and second transistors such that:
 a drain of the first transistor is coupled to a gate of the fourth transistor via a first capacitor; 
 a drain of the second transistor is coupled to a gate of the third transistor via a second capacitor; and 
 the drain of the first transistor is connected to a source of the third transistor, the drain of the second transistor is connected to a source of the fourth transistor; 
 the drain of the first transistor is coupled to a gate of the second transistor directly or via a third capacitor; and 
 a source of the first transistor is connected to a first inductor and a source of the second transistor is connected to a second inductor, and wherein a gate of the first transistor is configured to receive the single-ended input signal. 
   
     
     
         2 . A low noise amplifier for converting a single-ended input signal to a differential output signal, the amplifier comprising:
 a first transistor, configured in common-emitter mode, to receive the single-ended input signal and generate a first part of the differential output signal;   a second transistor, configured in common-emitter mode, to generate a second part of the differential output signal; and   a third transistor and a fourth transistor, and wherein the third transistor and forth transistor are cross-coupled and connected to the first and second transistors such that:
 a collector of the first transistor is coupled to a base of the fourth transistor via a first capacitor; 
 a collector of the second transistor is coupled to a base of the third transistor via a second capacitor; and 
 the collector of the first transistor is connected to an emitter of the third transistor, the collector of the second transistor is connected to an emitter of the fourth transistor; 
 the collector of the first transistor is coupled to a base of the second transistor directly or via a third capacitor; and 
 an emitter of the first transistor is connected to a first inductor and an emitter of the second transistor is connected to a second inductor, and wherein a base of the first transistor is configured to receive the single-ended input signal.