Switched-capacitor elliptic filter

An electronic elliptic filter comprising:

• an input means connected to an input voltage source to be filtered, said input means including a first switched capacitor means;
• a first integrating operational amplifier having a non-inverting input connected to a first voltage source, an inverting input connected to said input means, and an output terminal;
• a first feedback means including a first capacitor connected between said inverting input terminal of said first integrating operational amplifier and said output terminal of said first integrating operational amplifier;
• a second feedback means including a second switched capacitor means connected between said inverting input terminal of said first integrating operational amplifier and said output terminal of said first integrating operational amplifier;
• a second integrating operational amplifier having a non-inverting input terminal connected to said first voltage source, an inverting input terminal, and an output terminal;
• a third feedback means including a second capacitor connected between said inverting input terminal of said second integrating operational amplifier and said output terminal of said second integrating operational amplifier;
• a first means for connecting, including a third switched capacitor means, connected between said output terminal of said first integrating operational amplifier and said inverting input terminal of said second integrating operational amplifier;
• a fourth feedback means including a fourth switched capacitor means connected between said inverting input terminal of said first integrating operational amplifier and said output terminal of said second integrating operational amplifier;
• a third integrating operational amplifier having a non-inverting input terminal connected to said first voltage source, an inverting input terminal, and an output terminal;
• a fifth feedback means including a third capacitor connected between said inverting input terminal of said third integrating operational amplifier and said output terminal of said third integrating operational amplifier;
• a sixth feedback means including a fifth switched capacitor means connected between said output terminal of said third integrating operational amplifier and said inverting input terminal of said third integrating operational amplifier;
• a second means for connecting including a sixth switched capacitor means connected between said inverting input terminal of said third integrating operational amplifier and said output terminal of said second integrating operational amplifier;
• and
• a fourth capacitor connected between said output terminal of said first integrating operational amplifier and said inverting input terminal of said third integrating operational amplifier,
• wherein each of said first, second, third, fourth, fifth and sixth switched capacitor means includes two MOSFET switching devices driven by a first clock signal representing a first phase of an alternating two phase clock source and two additional MOSFET devices driven by a second clock signal complementary to said first clock signal whereby stray capacitances in the system are grounded and do not affect the integration by the operational amplifiers, whereby an analog voltage from said input source is converted into a sampled data signal and an output voltage is produced from said third integrating operational amplifier, said output voltage containing only those frequencies in a preselected pass band.