Audio Voltage Amplifier:
The output of detector which is Audio frequency signal is amplified with respect to voltage. It is applied
to Power amplifier.
The amplified audio signal is further amplified by a power amplifier to get a specified power level. Then
it is given to the loudspeaker with sufficient power to drive the loud speaker.
The loudspeaker converts the audio signal into sound signal.
Each Block Explanation in detail
RF Section: The RF signal received through antenna and fed to the RF section. This circuit block
performs two main functions:
(i) Tuning or Pre-selection: Broadband tuning is applied to the RF stage. The purpose of this stage is to
Select desired signal frequency and reject unwanted signal frequency i.e., image frequency. It must also
be able to track the local oscillator so that as the receiver is tuned, so the RF tuning remains on the
(ii) Amplification: In terms of amplification, the level is carefully chosen so that it does not overload the
mixer when strong signals are present, but enables the signals to be amplified sufficiently to ensure a
good signal to noise ratio is achieved.
The advantages of having an RF amplifier are as follows
1. Greater gain, i.e., better sensitivity
2. Improved image-frequency rejection
3. Improved signal-to-noise ratio
4. Improved rejection of adjacent unwanted signals, i.e., better selectivity
5. Better coupling of the receiver to the antenna (important at VHF and above)
6. Prevention of spurious frequencies from entering the mixer and heterodyning there to produce an
interfering frequency equal to the IF from the desired signal
7. Prevention of re-radiation of the local oscillator through the antenna of the receiver
Prepared by –M.Adiseshaiah,M.Tech,(Ph.D)., Assistant Professor , DVR&Dr HS MIC College of Technology