[sdiy] OTA-based variable inductance

Phil Macphail phil.macphail at liivatera.com
Fri Nov 3 09:47:01 CET 2023

Gm-C filters were popular in IC design in the late 90’s as the gm is easy to trim to compensate for capacitor variation. They were used for baseband filtering in IQ systems as well as bandpass filters in low-IF systems - these are particularly interesting as they use gyrators to couple capacitors in a pair of quadrature-driven filters to shift the centre-frequency away from DC and reject negative frequencies (in a tunable way). 
The IEEE Journal of Solid State Circuits is full of these designs if you search “gm-C filter”, but the limited dynamic range and noise has made these less fashionable now. 


> On 3. Nov 2023, at 06:38, Lanterman, Aaron D via Synth-diy <synth-diy at synth-diy.org> wrote:
> I’m sitting in on my colleague Jennifer Hasler’s class on analog VLSI design this semester. The other day in lecture she showed really interesting circuit I hadn’t seen before, a gyrator using OTAs instead of op amps:
> https://youtu.be/k1OCvp3HDXw
> Aaron Lanterman, Prof. of ECE, Georgia Tech
> My blog on Education and Innovation: https://edupocalypsenow.wordpress.com <https://edupocalypsenow.wordpress.com/>
> My blog on Electronics and Programming: https://lantertronics.blogspot.com <https://lantertronics.blogspot.com/>
> My YouTube channel on Electronics and Programming: https://www.youtube.com/c/lantertronics
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