583
Audio ICs
Band-pass filter for spectral analyzers
BA3830S
The BA3830S is a 61 band band-pass filter for spectral analyzer displays with internal recording indicator output. All
of the capacitors comprising the filter are internal capacitors, making it possible to significantly reduce the number of
attached components. This enables configuration of compact sets with a high level of reliability.
Applications
CD radio cassette players, mini-components, car stereos
Features
1) Six internal band-pass filters for spectral analyzers
2) Internal input/output for recording indicators 3) Internal capacitors reduce the number of attach-
ments.
Absolute maximum ratings (Ta = 25C)
Recommended operating conditions (Ta = 25C)
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Audio ICs BA3830S
Block diagram
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Audio ICs BA3830S
Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 5V, RL = 10MΩ, Rφ1 = 270kΩ,
Rφ2 = 270kΩ)
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Audio ICs BA3830S
Measurement circuit
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Audio ICs BA3830S
Circuit operation
(1) LINE and REC input circuits
The LINE and REC input circuits are configured as differ-
ential amplifiers, and the gain can be set to any desired
value using an external resistor . The input impedance is
determined by the external resistor.
(2) Bias circuit
A bias voltage of VCC/2 is applied to each of the circuits.
Since the output stage uses a push-pull configuration, a
stable bias source can be obtained.
(3) BPF circuit
This is a circuit that selects the required frequency com-
ponent from the input signal and amplifies it. With this
configuration, no external capacitor is needed. In addi-
tion, the center frequency is set based on the current, so
f01 and f02 to f06 can be set individually , using separate ex-
ternal resistors (pins1 and 2).
Q is set to 4.5V (Typ.).
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Audio ICs BA3830S
(4) DET circuit
This circuit carries out phase detection on the signal se-
lected and amplified by the BPF, and holds it at the peak
level. It is configured so that all of the capacitors are inter-
nal.
The charge that was charged by the internal capacitors
in the DET circuit is set to be discharged at 75ms/V
(T yp.), but in order to eliminate any effects of disparity, a
reset circuit is also included.
(5) Output section circuit
The signal level held at peak level by the DET undergoes
V/I conversion and is output. Since the next stage sup-
ports MOS (high-input impedance), there is a resistance
of 33.9kΩ (44.3kΩ for REC output only) between the out-
put pin and the GND in the IC, so the output value
changes based on the input impedance.
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Audio ICs BA3830S
Application example
Operation notes
(1) Precautions concerning the load resistance
The various characteristics were measured at the output
resistance value of 10MΩ noted in the specifications
manual. Moreover, because the output of this IC sup-
ports the MOS configuration, be aware that it is current
output, and the output changes depending on the input
impedance at the next stage.
(2) Precautions concerning the RESET capacitor
If the reset function is to be used, a capacitor of at least
3300pF is required for RESET C (pin 7). Failing to con-
nect this capacitor can result in erroneous displays, so
make sure a sufficient capacitance is provided.
(3) Precautions concerning the coupling capacitor
When determining the polarity of the input electrolytic
coupling capacitor, the potential relation with the other
end of the coupling must be taken into consideration.
External dimensions (Units: mm)
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Audio ICs BA3830S
Electrical characteristic curves
