2hz low pass filter
To perform 0.05Hz cut-off LPF, in general it is difficult if no external components are allowed.
For discrete time approach, eg switched cap, you will need a low sampling clock and small switched capacitor. Low sampling clock itself will consume large area.
For continuous time approach, eg gm-C filter, you will need a very low gm linear OTA, which is at nA/V range. This requires nA range current biasing. Some low gm techniques need to apply and transistor may need to operate at weak inversion.
You may look for the following papers if you decided to go for continuous time approach:
1. A 60-db dynamic-range CMOS sixth-order 2.4-hz low-pass filter for Medical Applications, IEEE Transactions on Circuits and Systems -II, Vol 47 No.12 Dec 2000
2. Transconductance Amplifier Strucutres with very small transconductances: A comparative design approach, IEEE Journal of Solid-State, Vol 37 No.6 June 2002