Voltage level shifting circuit

Abstract

An integrated level shifter circuit converts an input signal having a first voltage potential to an output signal having a second voltage potential. The level shifter circuit provides circuit operation between the sections when the voltage potential of the input logic signal is converted to the output logic signal having lower voltage potential. For logic signals transmitted between sections of an integrated circuit operating with different supply voltages. The level shift circuit for each input includes two transistors and a voltage divider circuit having two resistors in series. The values of the resistors are selected to yield a desired output voltage at a node between the two resistors. In effect, the resistors lessen the a full 0.9 volt diode drop to yield a level shift which is a fraction of a diode drop. A capacitor in parallel with the resistor provides a path for AC signals and increases both the speed and bandwidth of the level shifter.

What is claimed is:  
     
         1 . A current-mode level shifting circuit comprising: 
 a first and a second input terminal;    a first and a second transistor each having a collector, a base and an emitter, the collectors of the two transistors being coupled to a common voltage terminal, the base of the first and second transistor being coupled to the first and second input terminal respectively; the base of each of the first and second transistor being coupled to a voltage divider circuit, each voltage divider circuit comprising a first and a second resistor in series between the respective base and emitter of respective transistors, a node between each first and second resistors in series being output nodes;    a differential pair of transistors; and,    two load circuits comprising a resistive circuit element in parallel with a circuit element for conducting current without affecting a voltage drop thereacross in a substantial manner, each load circuit coupled to a collector of the differential pair for providing a substantially constant voltage less than a circuit supply voltage at the respective collectors in operation, wherein each voltage divider has a capacitor connected in parallel with one of the first and second series resistors.    
     
     
         2 . A load circuit for provision of current from a source to a high-speed circuit comprising: 
 a first port for communication with the source;    a second port for communication with the high-speed circuit;    a resistor electrically connected between the first and second port providing a first path of current flow in a first mode of operation of the load circuit; and,    a diode electrically connected between the first and second port, wherein the diode is coupled in parallel to the resistor for providing a second path of current flow from the source to the high speed circuit when the diode is switched for conducting current.    
     
     
         3 . A load circuit for provision of current from a source to a high-speed circuit as defined in  claim 2 , wherein the high-speed circuit is used for mobile wireless applications.  
     
     
         4 . A load circuit for provision of current from a source to a high-speed circuit as defined in  claim 2 , wherein in a first mode of operation substantially all current is provided via the first path of current flow.  
     
     
         5 . A load circuit for provision of current from a source to a high-speed circuit as defined in  claim 2 , wherein in a second mode of operation current is provided via the first path and the second path of current flow, a fixed current provided via the first path of current flow.  
     
     
         6 . A load circuit for provision of current from a source to a high-speed circuit as defined in  claim 2 , wherein the diode comprises a Schottky diode.  
     
     
         7 . A load circuit for provision of current from a source to a high-speed circuit as defined in  claim 2 , wherein the source comprises a battery.  
     
     
         8 . A method of provision of current from a source to a high-speed circuit comprising the steps of: 
 receiving the current from the current source via a first port;    transmitting the current in a first mode of operation via a resistor to a second port connected to the high-speed circuit when a voltage drop between the first and the second port is less than a switching voltage of the diode; and,    transmitting the current in a second mode of operation via a resistor and a diode connected in parallel thereto, to the second port when a voltage drop between the first and the second port exceeds a switching voltage of the diode.