Description:

A novel flicker noise cancellation scheme is proposed, where the bias current is switched instead of input. Current output of the proposed transconductor is Gm*Vin, where instead of vin, Gm is switched every cycle from +Gm to -Gm. This allows for very high impedance input stage without explicit chopping switches. Makes direct connection to high impedance sensors possible without need of buffers and source followers.

Block Diagram:

Target Performance:

Complete (or better than simulation) cancellation of flicker noise.

Why it needs to be fabricated:

The reason why we want to tapeout this circuit is because the way flicker is modeled in BSIM transistor models (even advanced ones), doesn't allow us to fully validate the concept. In BSIM models, the flicker noise PSD changes directly and instantaneouly as a function of bias current, which we believe is not real. This makes it hard to validate the idea on simulation alone. In simulations, it shows some improvement of flicker noise but not complete cancellation. We believe it should cancel more and hence needs to be verified in Silicon.

References:

Although there are papers in which one pair is take offline and reset while other pair is used and they are switched every cycle, we have not seen Gm flipping technuque being proposed. The closest paper we know of are:

1. S. L. J. Gierkink, E. A. M. Klumperink, E. van Tuijl and B. Nauta, "Reducing MOSFET 1/f noise and power consumption by "Switched biasing"," Proceedings of the 25th European Solid-State Circuits Conference, 1999, pp. 154-157.
2. E. A. M. Klumperink, S. L. J. Gierkink, A. P. van der Wel and B. Nauta, "Reducing MOSFET 1/f noise and power consumption by switched biasing," in IEEE Journal of Solid-State Circuits, vol. 35, no. 7, pp. 994-1001, July 2000, doi: 10.1109/4.848208.

Team Members:

1. Jyotindra Shakya (Originally from Nepal)
2. Emanuel Caceres (Originally from Argentina)