Classification of Power Amplifiers Series-fed Class A Power Amplifiers Transformer Coupled Class A Amplifiers

Transcription

1 lassificatin f wer Amplifiers Series-fed lass A wer Amplifiers Transfrmer upled lass A Amplifiers 1

2 lassificatin f wer Amplifiers lass A peratin v Q Q I 1 Q In lass A peratin, shuld be flwing the whle cycle (p) Q pint is at the center f the perating range. >0 Here 1 and prvide required fr class A peratin. Q pint is at the center f the perating range. > lectrnic ircuit Analysis

3 lass A wer Amplifiers n:1 I v I v 1 1 Series-fed lass A wer Amplifier Transfrmer upled lass A wer Amplifier Here pwer frm is cnverted int utput pwer in lectrnic ircuit Analysis 3

4 lass peratin I 1 v Q Q =0 Q In lass peratin, shuld be flwing half cycle (p) Q pint is at cutff ( =0) f the perating range. Q =0 Here 1 prvides required =0 fr class peratin. Q pint is at the cutff f the perating range. = lectrnic ircuit Analysis 4

5 lass wer Amplifiers Q 1 in Q OT lass wer Amplifier Output Transfrmer-ess - O lass wer Amplifier Output apitr-ess Transfrmer upled lass wer Amplifier Here pwer frm is cnverted int utput pwer in lectrnic ircuit Analysis 5

6 lass A peratin Q D v 180 >180 Q Q In lass A peratin, shuld be flwing mre than half cycle (>p) Q pint is at small amunt abve cutff ( >0) f the perating range. Here and dide D prvides required small fr class A peratin. Q pint is abve the cutff f the perating range. Q >0 Q > lectrnic ircuit Analysis 6

7 lass A wer Amplifiers D D D D in Q 1 Q D OT lass A wer Amplifier Output Transfrmer-ess - O lass A wer Amplifier Output apitr-ess Transfrmer upled lass A wer Amplifier Here pwer frm is cnverted int utput pwer in lectrnic ircuit Analysis 7

8 lass peratin Q =0 < 0 v Q = 0 < 0 Q - In lass peratin, shuld be flwing less than half cycle (< p) Q pint is at belw cutff ( < 0) f the perating range. < 0 Here and prvides required belw cutff fr class peratin. Q pint is belw the cutff f the perating range. Q < lectrnic ircuit Analysis 8

9 lass wer Amplifiers Q =0 A v =0 I Tuned lass F wer Amplifier adi Frequency Amplifier Here pwer frm is cnverted int utput pwer in lectrnic ircuit Analysis 9

10 lass D wer Amplifiers 0 t Sawtth generatr Amplifier w-pass Filter 0 t 0 t Input signal wave Feedbk Output signal wave I cnducting nly when digital versin f the input wave is high ---- ASS-D peratin. digital switching f the input wave fficiency is very high = ver 90% high lw lectrnic ircuit Analysis 10

11 Series-fed lass A wer Amplifiers v / Q Q I 1 () Q Maximum level Any level At max imum level (max) (max) (max) I 8 Q % At any level I Q lectrnic ircuit Analysis 11 8

12 Transfrmer upled lass A wer Amplifiers n:1 v /n Q n Q I Q = 1 () At max imum level (max) (max) (max) I 4 8n Q 8n % lectrnic ircuit Analysis At any level n I Q 8n 1

13 xample: : Transfrmer upled class A is perating with =10, =8, and transfrmer turn rati n=3. Measurements at gives min=1.7 and max=18.3,and measurements at gives min=5ma and max=55ma. Find (a),(b) (c) (d) (e) efficiency at that mment. 10 3:1 v () =8 I 1 At any level (a) (c) (d) (e) (b) 1 3 n I Q ma 1.15W % W O lectrnic ircuit Analysis 13