The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> High-Speed I/O Design >> Active inductor for high speed operation (> 12GHz) in 16nm finfet process
https://designers-guide.org/forum/YaBB.pl?num=1433208812

Message started by Larry_80 on Jun 1^st, 2015, 6:33pm

Title: Active inductor for high speed operation (> 12GHz) in 16nm finfet process
Post by Larry_80 on Jun 1^st, 2015, 6:33pm

Hi,
I am just wondering if anyone can comment on challenges faced in making a relatively high quality active inductor in the 16nm finfet process node? From what i heard it is tough to make considering large area and the variation associated with the design. Please kindly comment on challenges you have encountered and how you have been able to overcome them.

Title: Re: Active inductor for high speed operation (> 12GHz) in 16nm finfet process
Post by loose-electron on Jun 15^th, 2015, 1:02pm

please explain the concept of an "active" inductor

Title: Re: Active inductor for high speed operation (> 12GHz) in 16nm finfet process
Post by wave on Jun 15^th, 2015, 3:12pm

loose-electron wrote on Jun 15^th, 2015, 1:02pm:

please explain the concept of an "active" inductor

LE - think of the local Feedback in a Source Follower (or Emitter Follower). You need to include Cgs and resistance before the gate.
When Cgs shorts out, and R_G > (1/gm), you have larger Z at higher frequency.

Often a single stage amp, or more likely here, a differential CML has resistor plus active inductor loads for higher frequency gain.

Wave

Title: Re: Active inductor for high speed operation (> 12GHz) in 16nm finfet process
Post by loose-electron on Jun 17^th, 2015, 1:53pm

mathematical equivalence or active circuit that performs like an inductor - ok that make sense thanks for the :) feedback

Title: Re: Active inductor for high speed operation (> 12GHz) in 16nm finfet process
Post by bharat on Aug 1^st, 2015, 9:12am

Larry_80 wrote on Jun 1^st, 2015, 6:33pm:

LE -- it is Gyrator ( RC LPF at the input is seen as HPF).

Larry_80 --
Pros:
1. Better than Resistance. The source degeneration with resistive load is 2 pole one zero system. Replacing resistive load with active inductor makes it 3 poles and 2 zeros system. This improves peaking and adds linearity to overall gain function.

Cons:
1. Noise of active inductor is higher ( noise folding) and may go beyond overall rms noise spec
2. Unlike simple resistance, maintaining the common mode is challenging but use of replica bias might help.

Thanks
-Bharat

Title: Re: Active inductor for high speed operation (> 12GHz) in 16nm finfet process
Post by loose-electron on Aug 18^th, 2015, 1:01am

Do some research on gmC filters and transconductor circuits.