This paper involves the design and integration of an ultra-low power consumption Amplitude Shift Keying (ASK) demodulator and a digital Manchester decoder for biomedical applications. The ASK demodulator is based on a common source (CS) self-biased envelope detector (ED) with a double feedback loop, succeeded by a static comparator featuring constant transistor bias with a native transistor. While the digital Manchester decoder performs clock and data recovery. The practical implementation of the work is validated through simulations, executed on a standard 65 nm CMOS technology with a 50 Kbps data rate and a carrier frequency of 570 MHz. The average current drawn from a 2.5 V power supply is less than 800 nA while the circuit operates under RF variations and modulation indices ranging from 13.5% to 100%.