Apparatus and methods for biasing low noise amplifiers

Abstract

Apparatus and methods for biasing low noise amplifiers are provided herein. In certain configurations, a low noise amplifier (LNA) includes a transconductance device configured to amplify a radio frequency signal received from an input node, a cascode device electrically connected between an output node and the transconductance device, a first biasing resistor electrically connected between the input node and a ground node, a second biasing resistor electrically connected between the output node and the input node, and a current source electrically connected in series with the cascode device and the transconductance device.

What is claimed is: 
     
         1 . A low noise amplifier comprising:
 a transconductance device configured to amplify a radio frequency signal received from an input node;   a cascode device electrically connected between an output node and the transconductance device;   a first biasing resistor electrically connected between the input node and a ground node;   a second biasing resistor electrically connected between the output node and the input node; and   a current source electrically connected in series with the cascode device and the transconductance device.   
     
     
         2 . The low noise amplifier of  claim 1  wherein the transconductance device and the cascode device are bipolar transistors. 
     
     
         3 . The low noise amplifier of  claim 1  further comprising includes a third biasing resistor electrically connected between a collector of the cascode device and a base of the cascode device. 
     
     
         4 . The low noise amplifier of  claim 1  wherein the transconductance device and the cascode device are field-effect transistors. 
     
     
         5 . The low noise amplifier of  claim 3  further comprising a third biasing resistor electrically connected between a drain of the cascode device and a gate of the cascode device. 
     
     
         6 . The low noise amplifier of  claim 1  wherein the current source is configured to output a bias current that is substantially proportional to absolute temperature. 
     
     
         7 . The low noise amplifier of  claim 6  wherein the current source includes a p-type field-effect transistor and a proportional to absolute temperature circuit that controls a gate voltage of the p-type field-effect transistor. 
     
     
         8 . The low noise amplifier of  claim 1  further comprising a first inductor electrically connected between the current source and the cascode device. 
     
     
         9 . The low noise amplifier of  claim 8  further comprising a second inductor electrically connected between the transconductance device and the ground node. 
     
     
         10 . A packaged module comprising:
 a package substrate; and   a semiconductor die attached to the package substrate and including a low noise amplifier fabricated thereon, the low noise amplifier including a transconductance device configured to amplify a radio frequency signal received from an input node, a cascode device electrically connected between an output node and the transconductance device, a first biasing resistor electrically connected between the input node and a ground node, a second biasing resistor electrically connected between the output node and the input node, and a current source electrically connected in series with the cascode device and the transconductance device.   
     
     
         11 . The packaged module of  claim 10  wherein the transconductance device and the cascode device are bipolar transistors. 
     
     
         12 . The packaged module of  claim 11  wherein the low noise amplifier further includes a third biasing resistor electrically connected between a collector of the cascode device and a base of the cascode device. 
     
     
         13 . The packaged module of  claim 10  wherein the current source is configured to output a bias current that is substantially proportional to absolute temperature. 
     
     
         14 . The packaged module of  claim 13  wherein the current source includes a p-type field-effect transistor and a proportional to absolute temperature circuit that controls a gate voltage of the p-type field-effect transistor. 
     
     
         15 . A mobile device comprising:
 an antenna;   a front end system including a low noise amplifier having an input node configured to receive a radio frequency signal from the antenna and an output node configured to output an amplified radio frequency signal, the low noise amplifier including a transconductance device configured to amplify the radio frequency signal received from the input node, a cascode device electrically connected between the output node and the transconductance device, a first biasing resistor electrically connected between the input node and a ground node, a second biasing resistor electrically connected between the output node and the input node, and a current source electrically connected in series with the cascode device and the transconductance device; and   a transceiver configured to receive the amplified radio frequency signal.   
     
     
         16 . The mobile device of  claim 15  wherein the transconductance device and the cascode device are bipolar transistors. 
     
     
         17 . The mobile device of  claim 16  wherein the low noise amplifier further includes a third biasing resistor electrically connected between a collector of the cascode device and a base of the cascode device. 
     
     
         18 . The mobile device of  claim 15  wherein the current source is configured to output a bias current that is substantially proportional to absolute temperature. 
     
     
         19 . The mobile device of  claim 18  wherein the current source includes a p-type field-effect transistor and a proportional to absolute temperature circuit that controls a gate voltage of the p-type field-effect transistor. 
     
     
         20 . The mobile device of  claim 15  wherein the low noise amplifier further includes a first inductor electrically connected between the current source and the cascode device, and a second inductor electrically connected between the transconductance device and the ground node.