Broadcast Band Rf Amplifier Circuit

  
The circuit has a frequency response that ranges from 100 Hz to 3 MHz; the gain is about 30 dB. Field-effect transistor Ql is configured in the common-source self-biased mode; optional resistor R1 allows you to set the input impedance to any desired value. Commonly, it will be 50 . The signal is then direct-coupled to Q2, a common-base circuit that isolates the input and output stages and provides the amplifier`s exceptional stability. Last, Q3 functions as an emitter-follower, to provide low output impedance (about 50 ).
Broadcast Band Rf Amplifier Circuit - schematic

If you need higher output impedance, include resistor R8. It will affect impedance according to this formula: Rs ~ ^0lJT - 50. Otherwise, connect output capacitor C4 directly to the emitter of Q3.




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