Circuit and method of zero generation in a real-time filter

A method of filtering an input signal for providing a filtered output signal, comprising the steps of:

• summing an input signal and a feedback signal for providing a first summation signal;
• converting said first summation signal to a first current;
• integrating said first current and providing a first integrated voltage;
• summing said first integrated voltage and an amplified input signal and said feedback signal for providing a second summation signal;
• converting said second summation signal to a second current;
• integrating said second current and providing a second integrated voltage as said feedback signal;
• and
• summing said second integrated voltage and said amplified input signal for providing the filtered output signal.

A filter circuit responsive to an input signal for providing an output signal, comprising:

• a first summation circuit having first and second inputs and an output, said first input being coupled for receiving the input signal, said second input being coupled for receiving a feedback signal, said output providing a first summation signal;
• a first transconductance amplifier having an input coupled for receiving said first summation signal and having an output for providing a first current;
• a first capacitor coupled between said output of said first transconductance amplifier and a first node for integrating said first current and providing a first integrated voltage, said first node being coupled for receiving a first potential;
• a second summation circuit having first, second and third inputs and an output, said first input being coupled for receiving said first integrated voltage, said second input being coupled for receiving an amplified input signal, said third input being coupled for receiving said feedback signal, said output providing a second summation signal;
• a second transconductance amplifier having an input coupled for receiving said second summation signal and having an output for providing a second current;
• a second capacitor coupled between said output of said second transconductance amplifier and a second node for integrating said second current and providing a second integrated voltage as said feedback signal, said second node being coupled for receiving a second potential;
• and
• a third summation circuit having first and second inputs and an output, said first input being coupled for receiving said second integrated voltage, said second input being coupled for receiving said amplified input signal, said output providing the output signal of the filter circuit.