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AMPLIFIER COMPONENTS
VCC
the DC voltage that powers the amplifier
sets the DC operating
provides the energy for the output AC signal
RB1
RB2
DC bias potential divider to set the ‘Q’ point in conjunction with VCC
RE
emitter resistor to provide, due to the negative feedback effect, a stable ‘Q’ point
if component values change with age or temperature, transistor is replaced or transistor
parameters change due to age or temperature.
if unbypassed by a capacitor will reduce the ac voltage gain !!!!
CC1
ensures generator does not affect the bias (Q point of transistor Q1)
input transistor DC voltage does not affect the generator
CC2
ensures stage 1 and stage 2 bias remains the same when the 2 stages are interconnected
CC3
ensures the load does not affect transistor Q2 bias
to provide only ac output to the load
CE
to avoid stage 1 negative feedback due to RE reducing the voltage gain
VGEN represents the input signal voltage source (signal generator, microphone etc.)
RGen
represents the input source internal impedance / resistance
RL
represents the amplifier load ( resistor, loudspeaker, input resistance of a cascaded
stage etc.)
NOTE:
VGEN NOT required in the analysis of amplifier voltage gain
but required if actual voltages are needed
RGen
NOT required in the analysis of amplifier voltage gain
but required if actual voltages are needed
RGEN forms a potential divider with Rinput of amplifier
RL
EMT112:
Amplifier voltage gain is RL dependent
ANALOG 1
AMPLIFIER COMPONENTS
1
Prof R T KENNEDY
2004