Patent ID: 7057451

Claim:
A programmable/tunable active RC filter, comprising: a first controllable shunt device having an input terminal, a first output terminal and a second output terminal, wherein said input terminal of said first controllable shunt device is connected to a first input signal; a second controllable shunt device having an input terminal, a first output terminal and a second output terminal, wherein said input terminal of said second controllable shunt device is connected to a second input signal, and said second output terminal of said second controllable shunt device is connected to said second output terminal of said first controllable shunt device; a third controllable shunt device having an input terminal, a first output terminal and a second output terminal; a fourth controllable shunt device having an input terminal, a first output terminal and a second output terminal, wherein said second output terminal of said fourth controllable shunt device is connected to said second output terminal of said third controllable shunt device; a differential amplifier having two input terminals and two output terminals, wherein each of said two input terminals is respectively connected to each of said first output terminals of said first controllable shunt device, said second controllable shunt device, said third controllable shunt device and said fourth controllable shunt device, each of said two output terminals is respectively connected to each of said input terminals of said third controllable shunt device and said fourth controllable shunt device; and two capacitors, wherein each of said two capacitors is respectively connected to said two input terminals and said two output terminals of said differential amplifier for forming a RC filter and then being outputted from two output terminals of said two capacitors.