Question on Allen's Book

[sisching]

Hi

I have some questions on the page 401 of Allen's book (CMOS Analog Circuit Design, 2nd)

At the figure 7.4-8, this states that "the gate-source voltage of M3 is translated to the gate-source of M1 via the paht M4-M5-M6"

I cannot follow the step, could anyone express in detail?

Thx!!!

 

[Syukri]

The trick is at M7 and M6....current from M3 flows to them....
pictrure M3 like the current source and then M7 and M6 is the current mirror circuit...
with the same ratio and (especially width) the current is mirrored or similar at M7 and M6 and also transfered to M1.

This is my opinion...good luck

 

[pillar_chen]

v1 through inverter (M3, M4, M7) arrive at Vgs5 and then reach Vgs3 throuth inverter 2(m5, M6).

 

[sisching]

Then ...
why Vgs1 is equal to Vgs3?

 

[Syukri]

Well the transistor size is not mention... I assume that M1, M3,M7 and M6 is identical on size....same current is tranfered..

Transistor size determine the capacitance and resistance of the device. so same size transistor with same style of connection will have similar resistance. If both of then supplied with same value of current then the resulting voltage should be the same also.