Recent Advances on the Design of High-Gain Wideband Operational Transconductance Amplifiers

Abstract EN

Feed-forward techniques are explored for the design of high-frequency Operational Transconductance Amplifiers (OTAs).

For single-stage amplifiers, a recycling folded-cascode OTA presents twice the GBW (197.2 MHz versus 106.3 MHz) and more than twice the slew rate (231.1 V/μs versus 99.3 V/μs) as a conventional folded cascode OTA for the same load, power consumption, and transistor dimensions.

It is demonstrated that the efficiency of the recycling folded-cascode is equivalent to that of a telescopic OTA.

As for multistage amplifiers, a No-Capacitor Feed-Forward (NCFF) compensation scheme which uses a high-frequency pole-zero doublet to obtain greater than 90 dB DC gain, GBW of 325 MHz and better than 70∘ phase margin is discussed.

The settling-time- of the NCFF topology can be faster than that of OTAs with Miller compensation.

Experimental results for the recycling folded-cascode OTA fabricated in TSMC 0.18 μm CMOS, and results of the NCFF demonstrate the efficiency and feasibility of the feed-forward schemes.