A Linearization Technique for Differential OTAs

This brief presents an operational transconductance amplifier (OTA) linearization technique that is applied to a low-noise amplifier (LNA) and an OTA-C filter. Simulations show the effectiveness of the proposed technique on the LNA, whose noise and gain performance remain unaffected while the linearity is significantly improved. Measurements of the 80-MHz fourth order Butterworth OTA-C filter are also presented. It is implemented using six OTAs instead of eight, thus reducing the power consumption and area. The filter is implemented in 65-nm low-power CMOS, with a core area of 0.05 mm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol 2}$ </tex-math></inline-formula> and consumes 12.6 mA from 1.2 V supply. The measured in-band noise voltage is below 42 nV/<inline-formula> <tex-math notation="LaTeX">$\mathbf {\sqrt {Hz}}$ </tex-math></inline-formula>, and the measured third order intercept point improvement using OTA linearization is up to 17 dB in-band and about 3 dB out-of-band. Supply and temperature variation measurements on three samples show that the linearization is effective without a need for bias adjustment.

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