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YDA131-EZ View Datasheet(PDF) - Yamaha Corporation

Part Name
Description
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YDA131-EZ
Yamaha
Yamaha Corporation Yamaha
YDA131-EZ Datasheet PDF : 18 Pages
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YDA131
Description of operation functions
Refer to "Connection circuit example" on page 11, when reading the following descriptions.
Gain setting
This IC consists of the first stage inversion operational amplifier, and the fixed-gain digital power amplifier.
The gain of the digital power amplifier is fixed at 8 dB.
The gain of the first stage inversion operational amplifier is set with the resistance values of the input resistor (RI) and
feedback resistor (RF) as described by "Formula 1". To reduce pop noise, it is necessary to observe the restrictions
described in "Pop noise reduction function" on page 9. Use the feedback resistor (RF) of 10kor higher, because the
driving capability of the operational amplifier is limited.
In "Application circuit", input resistor (RI)=7.5kand feedback resistor (RF)=47kand the gain of the first stage inversion
operational amplifier is set at 16 dB, as described in "Figure 1: First stage inversion operational amplifier input circuit
example". Therefore, the total gain at this case is given as described below.
8dB (fixed gain of the digital power amplifier) + 16dB (gain of the first stage inversion operational amplifier) = 24dB
In the "Application circuit", low pass filter capacitor (CF) is added to limit the band width of the input signal, as described
in "Figure 1: First stage inversion operational amplifier input circuit example", whereby the value can be adjusted as
necessary. To limit the input DC current, DC cutting capacitor (CI) is added, whereby this capacitor and input resistor (RI)
constitute a high pass filter.
The cut off frequency fc of this high pass filter is set as necessary, and can be decided by "Formula 2".
Formula 1: Gain of first stage inversion operational amplifier Av(dB) = 20*log(RF/RI)
Formula 2:Cut off frequency fc(Hz) = 1/(2*π*RI*CI)
When low band boost function is needed due to a reason such as small diameter speaker, the low boost function can be
realized by making the circuit of the first stage operational amplifier as shown in "Figure 2: Low band boost circuit
example". For this circuit, the gain is increased by +3dB at the frequency fb of "Formula 3", and the low band boost
quantity Ab is decided by "Formula 4". At this time, the frequency characteristic is as shown in "Figure 3: Frequency
characteristic at low band boost".
Formula 3: Frequency at which the gain increased by +3dB fb(Hz) = 1/(2*π*RF*CB)
Formula 4: Boost quantity Ab(dB) = 20*log((RF+RB)/RF)
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