Benefits of Using VCO-OTAs to Construct TIAs in Wideband Current-Mode Receivers Over Inverter-Based OTAs

A filterless blocker-tolerant current-mode receiver using a voltage-controlled oscillator-based operational transconductance amplifiers (VCO-OTAs) for the baseband transimpedance amplifiers (BB TIAs) is presented as an alternative to inverter-based OTAs (inv-OTAs). Three key advantages of VCO-OTAs over inv-OTAs are a high-dc gain, a higher bandwidth for a given dc gain, and independent control of noise and the unity-gain bandwidth. These advantages are used to demonstrate power reduction in the BB TIAs, the low-noise transconductance amplifier, and the passive mixer LO drivers in the receiver. A design methodology for the choice of the VCO-OTA parameters in the context of a receiver design is illustrated with an example of a 20-MHz RF-channel bandwidth receiver operating at 2 GHz. Receiver simulation results indicate an improvement of up to 12 dB in blocker 1-dB compression point (B1dB) for slightly higher power consumption or up to 2.6× power reduction of the TIA resulting in up to 2× power reduction of the receiver for similar B1dB performance.