BA546 Просмотр технического описания (PDF) - ROHM Semiconductor
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BA546 Datasheet PDF : 6 Pages
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Audio ICs
FCircuit construction (See Fig. 2)
(1) Voltage amplification stage
This circuit is comprised of a differential amplifier (Q1 and
Q4), a constant current source (Q5), and an active load
(Q2 and Q3). This active load is the input to the pre-driver
(via Q8 and Q9).
(2) Pre-driver
The pre-driver is an earthed-emitter amplifier with tran-
sistors Q8 and Q9 forming a Darlington PNP transistor.
The Q9 collector load is the input impedance looking from
the base of Q14 and the constant-current load due to Q12.
(3) Idling loop
The idling loop is the Q13, Q10, Q11 and Q14 loop. The VBE
of Q13 is subtracted from the VF of Q10 and Q11 and is
biased by Q14.
(4) Power stage
The power stage is a quasi-complementary circuit made
up of a Darlington PNP transistor (Q13 and Q15), and an
NPN transistor (Q14).
BA546
(5) The AC gain is determined by the ratio between R6
(24kΩ) and RNF connected to pin 7. The formula is as fol-
lows:
24kΩ
GVC 20log
[dB]
RNF
Variation of GVC and THD with RNF is shown in Fig. 12.
FApplication example
The BA546 will generally be used as a power amplifier for
portable cassette players and similar equipment, and will
usually have a preamplifier before it, so insert the volume
control between the stages. The gain of the power stage
alone is determined by RNF. Use Fig. 12 to choose a value
for RNF that gives the required gain.
When RNF is 68Ω, the standard GVC is 50dB. When com-
bining the BA546 with an ALC-equipped preamplifier as
the previous stage, the control voltage for the ALC can
be taken from pin 4, and the power supply for the pream-
plifier from pin 9.
408
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