Current mode class-D power amplifiers for high efficiency RF applications

Optimized Current-Mode Class-D RF Power Amplifier for Software Defined Radio

“…Also, the practical amplifier is designed and operated to approach the performance of the ideal amplifier. Figure 1 shows the simplified schematic and ideal voltage and current waveforms of a Current-Mode class-D amplifier [5]. The CMCD amplifier is similar to the Voltage-Mode class-D amplifier with interchanged voltage and current waveforms.…”

Design of Class-D Power Amplifier for WSN Applications

“…The fundamental circuit and ideal voltage/currentwaveforms of a voltage mode class-D(VMCD) amplifier (sometimes referred to only as "class-D")areshown in Fig 1(a) and Fig 1(b), respectively [4,5] .By driving two transistorsout-of-phase, the voltage across the transistors is a squarewaveform alternating between V CC and zero.Ideally, sincethere is no overlap between voltage and current waveforms,efficiency of 100% can be achieved. However, if the transistorshave output shunt capacitance, this capacitance must be chargedor discharged to V CC or ground.…”

“…whereC DS is the drain-source capacitance and V DS is thedrain-source voltage when the transistor is turned on.Thisoutput capacitance lossbecomes the dominant loss mechanism athigh frequencies starting at hundreds of megahertz.This is oneof the reasons that class-D is not a popular gigahertz amplifier [4,5] . advantage of the CMCD architecture [5] .…”

CMOS Integrated Switched-Mode Transmitters for Wireless Communication

“…In that case the current approximates a square-wave, containing odd harmonics, while the drain voltage for each device approximates a half-wave rectified sine wave. It has been shown that a high efficiency can be achieved, assuming the amplifier can be designed for Zero Voltage Switching (Long et al, 2002;Kobayashi et al, 2001).…”