A digital to transconductance converter for nauta structure op-amps in 65nm CMOS

A 1.2 GHz bandwidth and 88 dB gain range analog baseband for multi-standard 60 GHz applications

“…In order to provide a linear 1-V pp output amplitude, the Nauta-G m [20,21,22,23,24,25] OTA with high transconductance efficiency and linearity is utilized as shown in Fig. 3(b).…”

Calibration of the Nauta structure differential OTA

“…This is hard to achieve unless further modifications are made to the Nauta structure. One way of achieving this is by replacing each inverter in the original structure with an array of tri-state inverters as seen in Figure 25 [28].…”

“…The gates of the control transistors are connected to a digital control signal, EN (where EN_bar is the EN signal after inversion), that can effectively enable or disable the inverter. If each inverter in Figure 12 (Inv1-Inv6) can be replaced by an array of tri-state inverters of varying sizes in parallel, where each individual tri-state inverter can be controlled by a separate control signal, a digital-totransconductance converter will we be formed [28]. Each control signal only needs to be toggled between high and low (VDD/GND) and therefore can be implemented using a binary/digital signal.…”

“…For this work two different modified, TDC based, Nauta structure prototypes were made available for experimentation and testing (schematics and physical prototypes). One implemented in 180nm technology, and one implemented in 65nm technology [28]. The two prototypes use different digital-to-transconductance converter structures described in Ch.…”

“…Just like the 180nm prototype, the 65nm version [28] also consists of digital to transconductance converters based on tri-state inverters. This version however, consists of equally sized DTCs, where all of the converters (FF, SC and CC) are made up of 10 individually controlled tri-state inverters.…”