CLASS D AMPLIFIER

2.  An amplifier is an electronic device used to
increase the magnitude of
voltage/current/power of an input signal.
 It takes in a weak electrical signal/waveform
and reproduces a similar stronger waveform at
the output by using an external power source.
 Depending on the changes it makes to the input
signal, amplifiers are broadly classified into
Current, Voltage and Power amplifiers.

3.  There are many classes of audio amplifiers:
 A, B, AB, C, D, E, and F.
 These are classified into two different
operating modes
 Linear and Switching.

4.  Linear Mode Power Amplifiers – Class A, B,
AB and C have an output that is proportional
to their input. Less efficient
 Switching Amplifiers- Class D, E and F. More
efficient

5.  A Class D audio amplifier is basically a
switching amplifier or PWM amplifier.
 Class D amplifier is a switching amplifier and
when it is in the “ON” state it will conduct
current but have almost zero voltage across the
switches, therefore no heat is dissipated due to
power consumption.
 When it is in the “OFF” mode the supply
voltage will be going across the MOSFETs, but
due to no current flow, the switch is not
consuming any power.

8.  PMW modulator
 Switching circuit
 Output low pass filter

10.  A comparator has two inputs, namely Input A
and Input B.
 When Input A is higher in voltage than Input
B, the output of the comparator will go to its
maximum positive voltage(+Vcc).
 When Input A is lower in voltage than Input
B, the output of the comparator will go to its
maximum negative voltage(-Vcc).

11.  Provides enough power gain to drive the
load
 Designed using MOSFETs
 Switching circuits should produce signals
that do not overlap. Otherwise shoot through
occurs
 The non-overlapping time is known as Dead
time

12.  We must keep the dead time as short as
possible to maintain an accurate low-
distortion output signal but must be long
enough to maintain both MOSFETs from
conducting at the same time
 A Schottky diode can be added in parallel to
the drain and source of the MOSFET to
reduce the losses through the MOSFET

13.  Output filter attenuates and removes the
harmonics of the switching signal frequency
 A 2nd order Butterworth filter is desired so
that we have a -40 dB/Decade roll-off
 The range of cutoff frequencies is between
20 kHz to about 50 kHz

14.  Suitable for portable devices
 Television sets and home-theatre systems.
 High volume consumer electronics
 Headphone amplifiers
 Mobile technology
 Automotive

16.  S.M.S.L AD 18
 Crown XLS 150
 NAD D3045
 Heaven 11 Billie
 Hegel H95
 Bel Canto C5i
 Lyngdorf TDAI 1120
 Lyngdorf SDA 2400
 Bel Canto REF600M
 Legacy Audio I-V2
 Bel Canto Black EX Integrated