Precision full-wave rectifier circuit for high-density, low-power implantable medical device

Abstract

A precision voltage rectifier comprises a source voltage input and a voltage reference. The rectifier comprises switching elements that, according to the sign of the source signal, change the connections to the inputs of a differential difference amplifier that is connected as a voltage inverter. Embodiments of the invention are fully-integrated and CMOS compatible with high-input impedance such that the invention can be operated in low-power situations. A preferred application involves the integration of several similar circuits in a high-density, low-power implantable medical device. Particular embodiments of the invention can be used to rectify nerve signals collected by electrodes for use in a system for manipulating a prosthetic device.

What is claimed is:  
     
         1 . A voltage rectifying circuit comprising: 
 a source signal input coupled to a first input of a polarity judgment circuit and to a first input of a switching circuit;    a reference signal input coupled to a second input of the polarity judgment circuit and to a second input of the switching circuit;    the polarity judgment circuit having an output connected to a first control input of the switching circuit;    the switching circuit having a first output connected to a first non-inverting input of a DDA, and a second output connected to a first inverting input of the DDA;    the reference signal connected to a second non-inverting input of the DDA; and,    the DDA having an output connected to a second inverting input of the DDA.    
     
     
         2 . A voltage rectifying circuit according to  claim 1 , wherein the switch circuit comprises an inverter having an input connected to the output of the polarity judgment circuit and an output connected to a second control input of the switching circuit.  
     
     
         3 . A voltage rectifying circuit according to  claim 2 , the switching circuit comprising: 
 a first switch set having a first input connected to the source signal, a second input connected to the reference signal, a control input connected to the output of the polarity judgment circuit, a first output connected to the first non-inverting input of the DDA, and a second output connected to the first inverting input of the DDA; and,    a second switch set having a first input connected to the source signal, a second input connected to the reference signal, a control input connected to the output of the inverter, a first output connected to the first non-inverting input of the DDA, and a second output connected to the first inverting input of the DDA.    
     
     
         4 . A voltage rectifying circuit according to  claim 2 , the switching circuit further comprising: 
 a first switching element having a source connected to the source signal, a gate connected to the output of the inverter, and a drain connected to the first non-inverting input of the DDA;    a second switching element having a source connected to the reference signal, a gate connected to the output of the polarity judgment circuit, and a drain connected to the first non-inverting input of the DDA;    a third switching element having a source connected to the source signal, a gate connected to the output of the polarity judgment circuit, and a drain connected to the first inverting input of the DDA; and,    a fourth switching element having a source connected to the reference signal, a gate connected to the output of the inverter, and a drain connected to the first inverting input of the DDA.    
     
     
         5 . A voltage rectifying circuit according to  claim 4 , wherein the switching elements are CMOS transistors.  
     
     
         6 . A voltage rectifying circuit in accordance with  claim 5 , wherein the DDA comprises: 
 current sources implemented using a cascode technique.    
     
     
         7 . A voltage rectifying circuit in accordance with  claim 3 , wherein the DDA comprises: 
 current sources implemented using a cascode technique.    
     
     
         8 . A voltage rectifying circuit in accordance with  claim 7 , wherein the polarity judgment circuit comprises a comparator.  
     
     
         9 . A voltage rectifying circuit in accordance with  claim 6 , wherein the polarity judgment circuit comprises a comparator.  
     
     
         10 . A voltage rectifying circuit in accordance with  claim 3 , wherein the polarity judgment circuit comprises a comparator.  
     
     
         11 . A method for rectifying a source signal, the method comprising: 
 comparing a voltage of a source signal voltage with a voltage of a reference signal;    when the voltage of the source signal is greater than the voltage of the reference signal, connecting the source signal to a first input of a first differential pair of a DDA, and connecting the reference signal to a second input of the first differential pair;    when the voltage of the source signal is less than the voltage of the reference signal, connecting the reference signal to the first input of the first differential pair and connecting a primary signal to the second input of the first differential pair;    connecting the reference signal to a second non-inverting input of a second differential pair of the DDA; and,    connecting an output of the DDA to a second inverting input of the second differential pair.    
     
     
         12 . A method for rectifying a source signal in accordance with  claim 11  wherein: 
 the first input of the first differential pair is a non-inverting input;  
 the second input of the first differential pair is an inverting input; and,  
 the primary signal is the source signal.  
 
     
     
         13 . A method for rectifying a source signal in accordance with  claim 11  wherein: 
 the first input of the first differential pair is an inverting input;  
 the second input of the first differential pair is a non-inverting input; and,  
 the primary signal is the source signal.  
 
     
     
         14 . A method for rectifying a source signal in accordance with  claim 11  wherein: 
 the first input of the first differential pair is a non-inverting input;  
 the second input of the first differential pair is an inverting input; and,  
 the primary signal is the reference signal.  
 
     
     
         15 . A method for rectifying a source signal in accordance with  claim 11  wherein: 
 the first input of the first differential pair is an inverting input;  
 the second input of the first differential pair is a non-inverting input; and,  
 the primary signal is the reference signal.  
 
     
     
         16 . A method for rectifying a source signal in accordance with  claim 15  comprising filtering the signal output of the DDA.  
     
     
         17 . A method for rectifying a source signal in accordance with  claim 12  comprising filtering the signal output of the DDA.  
     
     
         18 . A method for rectifying a source signal in accordance with  claim 13  comprising filtering the signal output of the DDA.  
     
     
         19 . A method for rectifying a source signal in accordance with  claim 14  comprising filtering the signal output of the DDA.