13.8A 3.3V-supply 120mW differential ADC driver amplifier in 0.18μm SiGe BiCMOS with 108dBc IM3 at 100MHz

Fully differential (operational) amplifiers (FDA) have become the preferred method of driving 1
^st
and 2
^nd
Nyquist zone signals into 100 to 500 Ms/s 12 to 16 bit ADCs. Previously the best performance (95dBc IM3 at 100MHz) came from designs in dielectrically isolated (Dl) Silicon Germanium complementary bipolar (CB) processes. These have not been developed at the 0.18μm geometry node, as the cost of shrinking these esoteric processes is not justified by the low volume markets they serve. Here 108dBc IM3 at 100MHz is obtained using a 0.18μm SiGe NPN-only RF BiCMOS. NPN-heavy circuits and a feedforward nested Miller architecture achieve this at 3.3V supply voltage and 36mA total supply current.