I have an off-chip filter and pre-amp circuit (see figure) that I would like to interface with the PSoC 3/5's ADC. This circuit buffers, bandpass filters (500 Hz–5 kHz by a four-pole multiple feedback Butterworth filter) and amplifies (1500×) biological signals (microvolt amplitudes).
Could I use PSoC's components (opamp, etc) to save space on my final board layout? This will be a low power (3V or less) design requiring 2-3 day battery life.
PSoC 3/5 has 4 opamps and 4 SC/CT (Switched Capacitance / Continuous Time) blocks.
The circuit which you are intending to build can be implemented on PSoC using the 4 opamps. The external components (resistors and capacitors) can be used as required.
The buffer (such as voltage follower) can be implemented using opamps or SC/CT blocks.