GHz and almost no changes in the rest of properties such as noise figure, current consumption, input return loss, and output return loss when compared with the 2-m GaInP/GaAs HBT LNA without interstage matching. The bandwidth of a cascode amplifier is usually limited by the output matching bandwidth. A resistor R C is used in the output stage to increase the output matching bandwidth and helps to stabilize the circuit. The amplifier demonstrated in this paper can be actually used in the range of 5.2 to 5.8 GHz for output return loss of at least 10 dB. The 2-m GaInP/GaAs HBT LNA without interstage matching has 13.5-dB power gain and 2.4-dB noise figure at 5.8 GHz while the 2-m GaInP/GaAs HBT LNA with interstage matching has 18.5-dB power gain and 2.43-dB noise figure at 5.8 GHz. The input return loss at 5.8 GHz is 18 dB for LNA without interstage matching and 10.5 dB for LNA with interstage matching. The output return loss at 5.8 GHz is 13.5 dB for LNA without interstage matching and 11 dB for LNA with interstage matching. There is still 5 dB power gain enhancement at 5.8 GHz with almost no changes in the rest of properties.
DISCUSSION AND CONCLUSION
A means to enhance power gain by inserting an interstage matching in a cascode LNA has been demonstrated. The matched LNA maintains the current reuse topology and has 5.5-dB power gain enhancement at 5.2 GHz without degradation in any other property. The method demonstrated here can be directly applied to any other technology. The 2-m GaInP/GaAs HBT LNA without interstage matching has 14-dB power gain and 2.37-dB noise figure at 5.2 GHz, while the 2-m GaInP/GaAs HBT LNA with interstage matching has 19.5-dB power gain and 2.22-dB noise figure at 5.2 GHz. The current consumption is 2.3 mA and voltage supply is 3.6 V.