An integrated receiver with channel selection and image rejection substantially
implemented on a single CMOS integrated circuit is described. A receiver front
end provides programable attenuation and a programable gain low noise amplifier.
Frequency conversion circuitry advantageously uses LC filters integrated onto the
substrate in conjunction with image reject mixers to provide sufficient image frequency
rejection. Filter tuning and inductor Q compensation over temperature are performed
on chip. The filters utilize multi track spiral inductors. The filters are tuned
using local oscillators to tune a substitute filter, and frequency scaling during
filter component values to those of the filter being tuned. In conjunction with
filtering, frequency planning provides additional image rejection. The advantageous
choice of local oscillator signal generation methods on chip is by PLL out of band
local oscillation and by direct synthesis for in band local oscillator. The VCOs
in the PLLs are centered using a control circuit to center the tuning capacitance
range. A differential crystal oscillator is advantageously used as a frequency
reference. Differential signal transmission is advantageously used throughout the
receiver. ESD protection is provided by a pad ring and ESD clamping structure that
maintains signal integrity. Also provided are shunts at each pin to discharge ESD
build up. The shunts utilize a gate boosting structure to provide sufficient small
signal RF performance, and minimal parasitic loading.