self-bias circuit design

[mohamis288]

Hello,
I have a question about the following self-bias circuit:

In the above circuit, m15-18 represents the start-up circuit.
How do these transistors help to start up the self-bias circuit?
what is their effect?
where does the current m15 and m16 go?
can you explain the general performance of above circuit?

I have simulated the above circuit in ADS, and I get to the following results
( I have simulated important node voltage for different amounts of rise time for dc supply):

results without startup circuit:


results with startup circuit:



It seems there is not a significant difference between these two circuits.

 

[FvM]

I guess your simulation has two problems.
1. Test without startup-circuit uses very fast (ns range) supply rise time. Thus the circuit starts fine by capacitive currents.
2. Start-up circuit has unsuitable transistor sizes. Current in start-up circuit should drop to zero but it doesn't, circuit is oscillating instead. Consider that X16 must be much weaker than X15.