Patent ID: 8737537

Claim:
An apparatus comprising: an input point receiving a frequency shift keyed (FSK) modulated signal; an output point; a differential amplifier coupled between said input and output points operative to amplify said FSK modulated signal, said differential amplifier including a pair of first and second transistors, said first transistor being configured as an emitter follower and said second transistor being configured as a common-base amplifier, said first transistor having a first collector, a first base, and a first emitter, said second transistor having a second collector, a second base, and a second emitter, said first base coupled to said input point; a band-pass filter coupled between said second collector and said output, said band-pass filter being tuned to substantially a center frequency of said FSK modulated signal; a negative feedback path coupled between said first collector and said first base; a first voltage divider coupled between first and second sources of reference potential operative to enable to regulate a voltage provided by said first source of reference potential and said FSK signal at said first base, said first voltage divider coupled to said first base; a capacitor coupled between said input point and said first base; and a bias circuit including a second voltage divider coupled between third and fourth sources of reference potential operative to enable to bias said second base.