Looking for resources about active inductors

[raymond_luo2003]

Hi, all,

Who has the comprehensive material on the active inductor, eg, by mos and capacitor? What's the advantage of this active inductor except the small area? Can active inductor offer the better performance than spiral or bonding wire inductor in some sense?

Thanks,
Raymond

 

[ramesh]

Re: Active Inductor

Spiral inductor causes EMI due to field created around it. In active inductor this very much reduced.

 

[Puppet1]

Re: Active Inductor

there is some discussion on active inductor in razavi's books:

try both

integrated circuits for optical communications

CMOS Analog Integrated Circuits

 

[goodboy_pl]

Re: Active Inductor

Active Inductors' Plus: lower area (a little or some times!), higher Q factors (1000's!)
Active Inductors' Minus: higher noise (due to active components), lower swing or dynamic range (due to active components), higher power consumption (for biassing active mosfets)

thus in RF applications like LNA, OSC which noise or swing is important passive inductors are the only solution,

passive inductors drawbacks are: larger chip area requirement, and substrate coupling; the first problem can be solved to some extent using stacked metal layers in series (decreases resonance freq also!) and second one can be overcomed using pattern ground shield beneth the inductor.

BEST!

 

[raymond_luo2003]

Active Inductor

Thanks good_boy_pl

You mentioned that active inductor can have a high Q up to 1000? Can give a example or some material?

Thanks,
Raymond

 

[guamak_menanak]

Re: Active Inductor

I'm also are trying to implement active inductor in my LNA design. I tried to use the active inductor as the input matching (inductive source degenerated) in the LNA design. The main problem are my NF is high (NF=9.8db) and the design is becoming unstable. The main reason is active inductor itself generate it's own noise and have it's own small signal charactersitic! This small signal can effect the performance of the LNA.

Therefore, can anyone give me some suggestion at which part that I can used active inductor on the LNA because my project is to implement Active Inductor on my design. To used active inductor as matching network is a bad design...anyone, help me

 

[dhlee]

Re: Active Inductor

The active inductor can't be used in the input matching network of LNA due to its noisy characteristics, and it is a basically small-signal equivalent inductor, so it's useless in large signal circuits like PA.

In my opinion, the active inductor can be used meritoriously for the RF chokes which need large inductance or tuning elements that can't be implemented by passive inductor.

How about using the active inductor in the series feedback element of gain-controlable LNA? The gain of LNA can be differed by the inductance of series feedback element, and It doesn't need large signal.

It will be interesting job~~ Good luck~~

 

[guamak_menanak]

Re: Active Inductor

How about using the active inductor in the series feedback element of gain-controlable LNA? The gain of LNA can be differed by the inductance of series feedback element, and It doesn't need large signal.

Can you explain more in detail how to use active L in the series feedback element of gain-controlable LNA? A paper or journal is very helpful!

Thanx is advance

 

[DoctorX]

Re: Active Inductor

Thanks good_boy_pl

You mentioned that active inductor can have a high Q up to 1000? Can give a example or some material?

Thanks,
Raymond

Try this. It is 665 tested on silicon.

 

[DoctorX]

Re: Active Inductor

you can refer to these 2 papers regarding active inductor and its usage.
Both are very good.
1) RF bandpass filter design based on CMOS active inductors
Yue Wu; Xiaohui Ding; Ismail, M.; Olsson, H.;
2) A novel CMOS fully differential inductorless RF bandpass filter
Yue Wu; Ismail, M.; Olsson, H.;

The Wu & Ismail circuit has an intrincally low Q of around 5, as the source of one of the MOSFET, which has a low impedance of 1/gm, is hooked up to the gyrator feedback node.

Try H. Xiao, Karsilayan and Schaumann's circuit, it is intrincally high Q, if this is desired. --- Yes, it is just in the previous message.

 

[wylee]

Re: Active Inductor

Try refering to my IEEE post

Active Inductor for Bandwidth Extension

 

[riajames]

Re: Active Inductor

can somebody tell me how to find the impedance of an active inductor circuit