Tunable device having a fet integrated with a bjt

Abstract

A device includes a field effect transistor (FET) integrated with at least a portion of a bipolar junction transistor (BJT), in which a back gate of the FET shares an electrical connection with a base of the BJT, and in which a reverse voltage can be applied to the back gate of the FET.

1 . (canceled) 
     
     
         2 . A radio frequency module comprising:
 one or more connections;   a die coupled to the one or more connections to allow for transfer of radio frequency signals to and from the die, the die including a transistor, the transistor including a base layer, an emitter layer, a source, a drain, at least one of a back gate or a front gate, and a channel formed at least partially in the emitter layer and configured to respond to a reverse voltage applied to the at least one of the back gate or the front gate to create a variable capacitance in the channel between the source and the drain.   
     
     
         3 . The radio frequency module of  claim 2  wherein the at least one of a back gate or a front gate includes both a back gate and a front gate that are separate nodes from one another. 
     
     
         4 . The radio frequency module of  claim 3  wherein the channel is further configured to respond to a first reverse voltage applied to the back gate and a second reverse voltage different from the first reverse voltage applied to the front gate to create the variable capacitance. 
     
     
         5 . The radio frequency module of  claim 3  wherein the transistor is a four terminal field effect transistor. 
     
     
         6 . The radio frequency module of  claim 2  wherein the transistor is configured to operate as a varactor. 
     
     
         7 . The radio frequency module of  claim 6  wherein the transistor is configured to operate as a varactor of a continuous tunable LC resonator. 
     
     
         8 . The radio frequency module of  claim 2  wherein the at least of a back gate or a front gate includes a back gate, and the reverse voltage ranges from −0.4 to −5.0 volts and is applied to the back gate. 
     
     
         9 . The radio frequency module of  claim 2  wherein the transistor is implemented using BiCMOS process technology. 
     
     
         10 . The radio frequency module of  claim 2  wherein the variable capacitance is achieved with a substantially linear capacitance-voltage response, at least over a predefined voltage range. 
     
     
         11 . A transistor comprising:
 a base layer;   an emitter layer;   a source;   a drain;   at least one of a back gate or a front gate; and   a channel formed at least partially in the emitter layer and configured to respond to a reverse voltage applied to the at least one of the back gate or the front gate to create a variable capacitance in the channel between the source and the drain.   
     
     
         12 . The transistor of  claim 11  wherein the at least of a back gate or a front gate includes both a back gate and a front gate that are electrically isolated from one another. 
     
     
         13 . The transistor of  claim 12  wherein the channel is further configured to respond to a first reverse voltage applied to the back gate and a second reverse voltage different from the first reverse voltage applied to the front gate to create the variable capacitance. 
     
     
         14 . The transistor of  claim 12  wherein the transistor is a four terminal field effect transistor. 
     
     
         15 . The transistor of  claim 11  wherein the transistor is a tunable radio frequency pass gate. 
     
     
         16 . The transistor of  claim 11  wherein the reverse voltage applied to the back gate or to the front gate ranges from −0.4 to −5.0 volts. 
     
     
         17 . The transistor of  claim 11  wherein the changes in variable capacitance are continuous over a range of the reverse voltage. 
     
     
         18 . The transistor of  claim 11  wherein the variable capacitance is achieved with a substantially linear capacitance-voltage response, at least over a predefined voltage range. 
     
     
         19 . A portable communication device comprising:
 an antenna;   a radio frequency module in communication with the antenna, the radio frequency module including a transistor, the transistor including a base layer, an emitter layer, a source, a drain, at least one of a back gate or a front gate, and a channel formed at least partially in the emitter layer and configured to respond to a reverse voltage applied to the at least one of the back gate or the front gate to create a variable capacitance in the channel between the source and the drain.   
     
     
         20 . The portable communication device of  claim 19  wherein the at least of a back gate or a front gate includes both a back gate and a front gate that are electrically isolated from one another. 
     
     
         21 . The portable communication device of  claim 20  wherein the channel is further configured to respond to a first reverse voltage applied to the back gate and a second reverse voltage different from the first reverse voltage applied to the front gate to create the variable capacitance.