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Home Electronic Applications in Communication Amplifiers Radio-Frequency Voltage Amplifiers
 
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Radio-Frequency Voltage Amplifiers

Several types of radio-frequency voltage amplifiers are possible; the tuned plate-tuned grid band-pass amplifier of Fig. 22 is widely used. The tube operates as a non-distorting amplifier. At the frequency of resonance the impedance in the load circuit is essentially pure resistance. The tube

radio-frequency transformer-coupled voltage amplifier
Figure 22. A radio-frequency transformer-coupled voltage amplifier with tuned primary and secondary.

acts like a generator in series with a plate resistance and a load resistance (Fig. 17).

The equations for the voltage amplification must be derived17 on the basis of coupled-circuit theory. For pentodes, the voltage gain at the resonant frequency is18

where gm is the grid-plate transconductance in mhos, k is the coefficient of coupling, fr is the resonant frequency in cycles, L1 and L2 are the self-inductances in henrys of the primary and the secondary, and Q1 and Q2 are the effective energy storage factors of the primary and the secondary. In circuits using pentodes the effective and actual Q are approximately equal.18


Home Electronic Applications in Communication Amplifiers Radio-Frequency Voltage Amplifiers

Last Update: 2011-05-30