BA3528AFP Datasheet, PDF (9/14 Pages) Rohm – Pre / power amplifier and motor governor for 3V headphone stereos

Audio ICs
FAttached components
(1) Preamplifier
If the closed-loop voltage gain (GVC) of the preamplifier
is below 30dB for a frequency of f = 1kHz, oscillation may
occur.
(2) Playback equalizer terminal (NAB)
The playback equalizer characteristics are determined
by the RC circuit connected between the output and NF
pins.
For the circuit in Fig. 9, with a closed-loop voltage gain
of GVC at an input frequency of 1 kHz, the relationships
between the values of the RC circuit components are as
follows:
C1 =
3180 10^–6
R1)200)10³
R2 = 2 R1 10^–GVC/20
BA3528AFP / BA3529AFP
the voltage difference between the pre-output and pin 22
will generate switching noise (a “pop” sound) when the
mute is switched on and off. To reduce the DC gain and
reduce this switching noise, we recommend that you
connect a resistor (R = 51 kΩ) as shown in Fig. 10. This
resistor reduces the gain of the circuit in the bass region
of the playback equalizer as shown in the graph in Fig.
11. By using different combinations of component values
for R1 and C1, it is possible to compensate for this effect
in the low-frequency region as shown in the graph in Fig.
12.
The equalizer can be switched on and off using the mute
amplifier. If equalization for metal tape is added, deter-
mine R3 as follows:
R3 = 1.4 R1
(3) Pre-mute switching noise
If you use the mute amplifier for pre-muting,
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