Single Ended Class A Power Amplifier with Transistor Load
The single ended class A power amplifier with transformer collector
load is shown in fig. the resistors R1,R2 and RE
form the biasing and stabilization network. The emitter bypass capacitor CE
offers low reactance path to the signal.
Here we use transformer in the collector load. In the
resistance coupled stage, the quiescent current passes through the load
resistance. Thus there appears a considerable waste of power due to drop across
load resistance due to passage of quiescent collector current which does not
contribute to the a.c. output power. In addition to this usually many
electronic systems have the loud-speaker as the load. The output impedance of
the amplifier is high. The loud-speaker voice coil impedance is of 8Ω. For maximum
has to be matched. This can be done by using a step-down transformer.
Single Ended Transformer Coupled Power Amplifier
Working:
The operating point is so selected that the transistor works
only in the linear portion of its characteristics. The input signal varies the
base current. This produces a variation in the collector current. As the
collector current in the primary of the output transformer varies, the induced
voltage in the secondary of the output transformer varies.
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