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| Gambar Rangkaian Power Amplifier BTL |
Audio amplifiers operate either in a
BTL (bridged) or single-ended ("normal") configuration. In the
single-ended setup, the output lead goes to the "hot" or "+" side of the
load (speaker or speaker box since we are talking audio) and the "-" or
"negative" side of the load is tied to a common ground shared with the
amplifier. In the BTL configuration, one amp is connected to the "+"
side of the speaker (load) and a second amp is connected to the "-" side
of the load. For this to work, the output signal from the second
amplifier must be a "mirror image" (identical in every respect, but 180
degrees out of phase) of the output from the first amp. The BTL
configuration is most often seen in low-voltage, battery-powered
applications (like cell phones or "walkman" type personal tape or cd
players etc) or in automotive applications over about 10 watts per
channel.
In the BTL
configuration, each amp drives half the load impedance. With the signals
being out of phase, the voltage swing across the load appears to be
doubled, and with each amp driving half the impedance the current is
doubled. In theory the bridged pair will produce 4 times the power into
the load that either amp acting alone could provide. In reality it
seldom works that well.
This
is an power amplifier circuit of a BTL system, which comprises a first
op-amp chip which outputs an output signal having a same phase as an
input signal input to a signal input terminal, a second operational
amplifier which outputs an output signal having an opposite phase to the
input signal, a voltage divider which generates a midpoint voltage of
the input signal, a first resistor connected between an output terminal
and a negative phase input terminal of the first operational amplifier,
second and third resistors connected in series between the negative
phase input terminals of the first and second operational amplifiers, a
fourth resistor connected between an output terminal and the negative
phase input terminal of the second operational amplifier, and an
impedance converter connected between a midpoint voltage node of the
voltage divider and a series-connection node of the second and third
resistors. (end of abstract)
List Componet:
R1, R2,R3, R4, R6..................... 10kOhm.
R3............................................. 20kOhm.
C1, C2, C3, C4........................... 10µF.
Catu daya (VCC) ±12 V.
