CLASSES Flashcards
most common type of amplifier topology
Class A
biased around the Q-point within the middle of its load line
Class A
conduct current over the full 360 degrees of the input cycle
Class A
one of the main disadvantages of Class A
output transistor of a class-A topology never turns “OFF”
excellent linearity, high gain and low signal distortion levels
Class A
create tremendous amounts of heat adding to their very low efficiency at around 30%, making them impractical for high-power amplifications
Class A
invented as a solution to the efficiency and heating problems
Class B
uses two complimentary transistors either bipolar of FET (“push-pull” type arrangement)
Class B
transistor device amplifies only half of the output waveform
Class B
there is no DC base bias current as its quiescent current is zero, so that the dc power is small and therefore its efficiency is much higher
Class B
This push-pull design of amplifier is obviously more efficient than Class A, at about 50%
Class B
combination of the “Class A” and the “Class B”
Class AB
both devices (T1&T2) are allowed to conduct at the same time around the waveforms
crossover point eliminating the crossover distortion problems
Class AB
two transistors have a very small bias voltage, typically at 5 to 10% of the
quiescent current to bias the transistors just above its cut-off point.
Class AB
efficiencies reach about 50% to 60%
Class AB
has the greatest efficiency but the poorest linearity
Class C
is heavily biased so that the output current is zero for more than one half of an input sinusoidal signal cycle with the transistor idling at its cut-off point.
Class C
the conduction angle for the transistor is significantly less than 180 degrees, and is
generally around the 90 degrees area.
Class C
much improved efficiency of around 80% to the amplifier, it introduces a very heavy
distortion of the output signal.
Class C
not suitable for use as audio amplifiers.
Class C
non-linear switching amplifier or PWM amplifier
Class D
boost both efficiency and output by using harmonic resonators in the output network to shape the output waveform into a square wave.
Class F
uses multiple power supply rails of various voltages and automatically switches between
these supply rails as the input signal changes
Class G
has two sets of complementary output switching devices arranged in a type of parallel push-pull configuration (one device switches the positive half of the waveform, while the other switches the negative half)
Class I
