Mumbai University > Computer Engineering > Sem 3 > Electronic Circuits and Communication Fundamentals

Marks: 5 Marks

Year: Dec 2015

1.A class C PA is used where large amounts of RF energy need to be generated with high efficiency.

2.Class C RF amplifiers must be used in conjunction with tuned circuits or cavities, which restore the amplified waveform through the flywheel effect.

3.The grounded-cathode class C amplifier is the building block of RF technology. It is the simplest method of amplifying continuous wave (CW), pulsed, and FM signals. The basic configuration is shown in Figure (a).

4.Tuned input and output circuits are used for impedance matching and to resonate the stage at the desired operating frequency. The cathode is bypassed to ground using low-value capacitors. Bias is applied to the grid as shown. The bias power supply may be eliminated if a self-bias configuration is used.

5.The typical operating efficiency of a class C stage ranges from 65% to 85%.

6.Figure (b) illustrates the application of a zero-bias triode in a grounded-grid arrangement.

7.Because the grid operates at RF ground potential, this circuit offers stable performance without the need for neutralization (at MF and below). The input signal is coupled to the cathode through a matching net-work. The output of the triode feeds a pi network through a blocking capacitor.