Folded Cascode Operational Transconductance Amplifier Research Articles

1-V power supply CMOS cascode amplifier

We design a folded cascode operational transconductance amplifier in a standard CMOS process, which has a measured 69-dB DC gain, a 2-MHz bandwidth, and compatible input- and output voltage levels at a 1-V power supply. This is done by a novel, current driven bulk (CDB) technique, which reduces the MOST threshold voltage by forcing a constant current though the transistor bulk terminal. We also look at limitations and improvements of this CDB technique.

A CMOS digitally programmable class AB OTA circuit

A new low-voltage CMOS digitally programmable operational transconductance amplifier (OTA) circuit is presented. The circuit utilizes simple class AB voltage buffers to provide a non-slew-rate-limited performance with low standby power consumption. The OTA can be digitally programmed to maintain a constant settling time for different load capacitors without increasing the standby power consumption, Experimental results from a 1.2-/spl mu/m chip and comparisons with the regular folded cascode OTA circuit are given. The proposed circuit power consumption is found to be less than one third of a regular folded cascode OTA when driving a load capacitance of 35 pF. For the same power consumption level of 240 /spl mu/A, the new circuit achieves a slew rate more than 10 V//spl mu/s while the traditional folded cascode fails to settle.

Symmetrically compensated fully differential folded-cascodeOTA

A symmetric compensation technique that improves the phase response for fully differential folded-cascode operational transconductance amplifiers (OTA) is proposed. Theory and simulated results show that the magnitude response and settling time for symmetrically compensated OTAs are also improved in comparison with those of compensated and typical OTAs.

Potential and modeling of 1-μm SOI CMOS operational transconductance amplifiers for applications up to 1 GHz

The potential of 1-/spl mu/m SOI complementary metal-oxide-semiconductor (CMOS) technology for the realization of operational transconductance amplifiers (OTAs) with transition frequencies in the gigahertz range is demonstrated. High-frequency device models, design guidelines and frequency limitations are detailed, as well as layout and technology improvements which can be used to boost the transconductance at high frequency and to reduce the source/drain-to-substrate capacitances. One-stage and folded-cascode OTA's have been realized to validate the design methodology.