High frequency differential filter with CMOS control

A programmable high frequency active filter for receiving a differential input signal and providing a differential output signal, said filter comprising:

• a differential amplifier comprising a first and second transistor, said first transistor having a first load resistor and being biased with a first bias current source, said second transistor having a second load resistor and being biased with a second bias current source;
• a capacitive network connected between the emitters of said first and second transistors for providing a frequency dependent differential voltage gain for said amplifier;
• a first MOS device connected with the drain and source between the emitter of said first transistor and said first current source;
• a second MOS device connected with the drain and source between the emitter of said second transistor and said second current source;
• a third MOS device connected with the source and drain between the collector of said first transistor and said first current source;
• and
• a fourth MOS device connected with the source and drain between the collector of said second transistor and said second current source;
• wherein the gates of all said MOS devices are connected to receive a digital control signal.