Temperature drift stabilized filter circuit

A filter circuit comprising:

• a capacitance amplifier circuit including an operational amplifier, an input capacitor having one terminal connected to an input terminal of the capacitance amplifier circuit and another terminal connected to a non-inverted input of said operational amplifier, an output resistance having a first terminal connected to an output of said operational amplifier, and a first feedback resistance having a first terminal connected to said non-inverted input and a second terminal connected to a second terminal of said output resistance, said output resistance and said first feedback resistance feeding output signals from said operational amplifier to said non-inverted input, said capacitance amplifier circuit producing an output at an output terminal thereof responsive to a voltage at said second terminal of said output resistance;
• a reference voltage circuit for generating a reference voltage at an output thereof, wherein said reference voltage circuit has a plurality of resistors, said reference voltage circuit being for outputting a divided voltage formed by said plurality of resistors as said reference voltage;
• and
• a series resistance having a first terminal connected to said output of said reference voltage circuit and a second terminal connected to said second terminal of said output resistance, for forming a CR circuit with said capacitance amplifier circuit to cut off a direct component of voltage input to said input terminal in combination with said capacitance amplifier circuit,
• wherein at least one of said plurality of resistors in said reference voltage circuit has a different temperature coefficient than at least one other resistor in said plurality of resistors, and
• a change in output voltage from said capacitance amplifier circuit due to a change of temperature is compensated by a drift of said reference voltage due to said different temperature coefficient responsive to said change of temperature.