a wireless communications mobile station includes at least one antenna and a rf transceiver containing a direct conversion receiver coupled to the antenna . the direct conversion receiver contains a low noise amplifier for amplifying a received rf signal and for outputting the amplified rf signal to a current switching down - conversion mixer . the down - conversion mixer has a first input node for receiving the amplified rf signal , a second input node for receiving a local oscillator signal for mixing with the amplified rf signal and an output node coupled to an input of an operational amplifier forming a low pass filter . in accordance with an aspect of this invention the low pass filter has a low pass pole generated by a resistor r and a capacitor c coupled in parallel in a feedback path of the operational amplifier , where a low pass comer frequency of the low pass filter is inversely proportional to the product of r and c . in a preferred embodiment at least the down - conversion mixer and the low pass filter are implemented as part of an integrated circuit , and the resistor and the capacitor are fabricated within the integrated circuit .