Do M1 and M2 mean cascode device?

[mpig09]

Hi all:

The attached file shows two cascode current
mirror structure.

Do M1 and M2 mean cascode device in the
two structure?

Do M3 and M4 mean current source in the
two structure?

Thanks for your reply.
mpig

 

[BradtheRad]

M1, M2, M3, M4 are all mosfets. The symbols are simplified. It's usual to assume enhancement-type.

From the position of the arrow, they appear to be N type.

Iin is a current source.

 

[mpig09]

Hi BradtheRad:

Thanks for your reply.

Because sometimes I hear the cascode current mirror are include
cascode device and current source.

So I wish to know how to distinguish which is cascode device and which is current source?

Thanks.
mpig

 

[Dominik Przyborowski]

Fig A - cascode current source, Fig B - Wilson current source.
The cascode device is only M2 on both schemes

 

[mpig09]

Hi Dominik Przyborowski :

Thanks for your reply.

Hi all:

If you have time,
One more question, the M3 and M4 is import in Fig A and Fig B?
I mean the ideal mirror (Iin = Iout) is based on M3 and M4?
So the vdsat of M3 and M4 need bigger than M1 and M2 or can
M2 into the triode region ?


Thanks.
mpig

 

[sarge]

Hi Dominik Przyborowski :

Thanks for your reply.

Hi all:

If you have time,
One more question, the M3 and M4 is import in Fig A and Fig B?
I mean the ideal mirror (Iin = Iout) is based on M3 and M4?
So the vdsat of M3 and M4 need bigger than M1 and M2 or can
M2 into the triode region ?


Thanks.
mpig

Hi,

For right operation all transistors must be in saturation region.
Cascode transistor uses for increasing output resistance (~ *gm2*r02).