低输出功率应用的E类CMOS功率放大器设计

1、 182Yuan Cheng,Li Zhiqun,Liu Jihua.and Wang Zhigongpact the circuit performance,especially the maximum PAoperating frequency.According to the rule of thumb,thewidth makingroeone tenth of the load resistor RL is a recommended initial value,which makes E髓about88%fromEq.(5.2.2Implementation of cuotal p

2、ower-controlOne important issue in the design is to implement theOHtptit powercontrol which is often required in practical ap-plications.Since the input signal provides only timing infor-marion in a class-E amplifier。the output power cannot becontrolled by changing the width of the input transistor

3、as iser control can be realized through a variablesupply imple-mented by a DC.DC converter.But in practical applica. tions.it is not easy to apply such an additional variable sup-ply and tIle DCDC converter circuit will consume extrapower which reduces the overall e1啊ciency.In this paper,a three-bit

4、 control pad(Bit2-BitO,as shown in Fig.2,is designed to change the output power digitally.With a control word“11r.the maximum power is available.while the minimum is at“000”.The control ofontput power is achieved by changing the duty cycle and the amplitude of the signal(which is the input to the ga

5、te of switch transistor SW.Since the turn.on resistance r.of switch transistor SW is a factor which degrades tlle output POwer and efficiency. changing the amplitude of K.will accordingly change the output power.Tlle amplitude of Vi。is controlled by the gain of the first stage.which can be altered b

6、y the widtll of the cascade transistor.Bit2controls the state of M22in Fig.2.men Bi匕is high.M22is paralleled into the circuit and the gain of the first stage increases.So is the amplitude of Vi。.Anotller method to control t11e power is by altering theCombining the change of amplitude and the dutv cy

7、cle of the input signal Vi。will give a wider adjustable output pow-el"range,and no more components are needed when com-pared wi山the traditional method.3Experimental Results and AnalysisFig.3Layout of the proposed ClassE PAWSN system where a0一dBm output POwer is typically needed.men using the di

8、gital controlling method.a DC.DCconverter which dissipates extra power is not needed.With the contr01word“ll l”。the maximum power is available。while the minimum iS at“000”.A power from一3.0t0 8.8dBm is obtained in mis case with the PAE from9%to 44%.as shown in Fig.6.Fig.4Pand PAE vs.input power Pi。、itll a1.2V supply voltage屹/v