So this is kind of vague question. I'm wondering what the approach to biasing MOSFETs in saturation is.
For the following circuit, I really have no specifications - I'm just trying to play around with it and get the highest gain I can.
Here's my usual approach for biasing:
- Set supply voltage (Vdd) to some reasonable value like 1.8V or 1.5V
- Have all MOSFETs ratios at default (I'm literally just trying to get them into saturation first)
- Start off by trying to bias the PMOS current source - one transistor at a time
- To do so, I would adjust the gate voltage for those PMOS devices starting off at something like 1V. But the issue arises that my drain source voltage for that device would be far too low and I would never be able to get it into saturation.
Again, I'm not looking for an exact answer here - just some guidance into what sort of approaches/mindset you have when biasing. Majority of the textbooks I've seen really seem to just gloss over biasing and I haven't actually seen a concrete trial/error example for it. They just assume it's always biased properly.