第九讲 Power Amplifiers 游飞博导/副教授，电子科技大学 feiyou@uestc.edu.cn 1
第九讲 Power Amplifiers 游飞 博导/副教授，电子科技大学 feiyou@uestc.edu.cn
12.1 General Considerations High voltage stress if directly powering the load Example:1 W to 50-Q load Amplitude=10 V,peak voltage=20 V(Swing from 0-20 V) It is impossible in a CMOS device. Figure 12.1.CS stages with (a)resistive,(b)current source,and (c)inductive load. T 多RL L1 C1 x H M Vin vn。H M1 幸R (a) (c
12.1 General Considerations High voltage stress if directly powering the load ◦ Example: 1 W to 50-Ω load ◦ Amplitude=10 V, peak voltage=20 V (Swing from 0-20 V) ◦ It is impossible in a CMOS device
12.1 General Considerations High Peak Current 20 V/500=400 mA(possible by increasing the size) Figure 12.2.Output voltage waveform in a Cs stage (a)when current flows from inductor to RL,(b)when current flows from RL to transistor. [View full size image] VoD X M M1 (3 (b)
12.1 General Considerations High Peak Current ◦ 20 V/50Ω=400 mA (possible by increasing the size)
12.1 General Considerations Matching Network Trading high current for high voltage .1 V dc supply to power 1 W output Vpp=2 V,4 A peak current. [View full size image] Matching 1:10 Network =1W. 50 M11 RT= -2 (a) b Figure 12.3.(a)Impedance transformation by a matching network,(b)realization by a transformer
12.1 General Considerations Matching Network ◦ Trading high current for high voltage ◦ 1 V dc supply to power 1 W output ◦ Vpp=2 V, 4 A peak current. Figure 12.3. (a) Impedance transformation by a matching network, (b) realization by a transformer
Effect of high current Increase the size of transistor to accommodate high current Increase the input capacitance Large driving power is needed Driver Output Stage Stage Matching Network 季RL LO
Effect of high current Increase the size of transistor to accommodate high current Increase the input capacitance Large driving power is needed