Amplifier circuit and analog-to-digital circuit using the same

Abstract

One or more input capacitors are connected to an inverting input terminal of an operational amplifier. Connected to the respective input capacitors are switches for on-off control of the input of an input signal, switches for on-off control of the input of another input signal, switches for on-off control of the input of a higher reference voltage and switches for on-off control of the input of a lower reference voltage. The switches for on-off control of the input of an input signal and the switches for on-off control of the input of another input signal are controlled by independent control signals.

1 . An amplifier circuit of a capacitive coupling type in which any of a plurality of input signals is inputted to one end of capacitance and a voltage appearing on the other end thereof is sampled, the amplifier circuit including: 
 a plurality of switches for use with input signals, provided respectively at path through which the plurality of input signals lead to one end of the capacitance; and    a switch for use with reference, provided at path through which a predetermined reference voltage signal leads to one end of the capacitance,    wherein each of the switches for use with input signals is directly connected to one end of the capacitance.    
   
   
       2 . An amplifier circuit according to  claim 1 , wherein the plurality of switches for use with input signals are respectively controlled by independent control signals.  
   
   
       3 . An amplifier circuit according to  claim 1 , wherein the capacitance is such that a plurality of capacitors are connected in parallel to an input terminal of the amplifier circuit.  
   
   
       4 . An amplifier circuit according to  claim 2 , wherein the capacitance is such that a plurality of capacitors are connected in parallel to an input terminal of the amplifier circuit.  
   
   
       5 - 20 . (canceled)