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YDA135-VZ View Datasheet(PDF) - Yamaha Corporation

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YDA135-VZ Datasheet PDF : 22 Pages
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YDA135
An "Example of application circuit" uses RI=8.2kΩ, RFB=39kΩ, RNFH=3.3kΩ and RNFL=2.4kΩ, which give total
gain (Av) that is calculated by using the following formula. With this setting, the input sensitivity is 150mVrms, where
the maximum output can be obtained when the input is 150mVrms.
Av (dB) = 20*log(2*39/8.2) + 8 + 20*log(1+3.3/2.4)
= 35.1 dB
This section explains how to set the gain for maximum level of the input signal. The relationship between the
maximum level of input signal, Vin (peak value), RI and RFB is given by the following formula. (When RNFH=3.3kΩ,
RNFL=2.4kΩ.)
Vin(peak value) = RI / RFB
For example, when setting as Vin = 300mVrms, the formula is ”300mVrms* √2 = RI / RFB”. When RFB = 39kΩ,
the value of RI is approximately 16kΩ. Set the value of RI as 2kΩ or less.
When setting the gain of the operational amplifier, which is initial stage, it is necessary to observe the restrictions
that are described in “Pop noise reduction functions”. Due to the limitation on operational amplifier driving
capability, it is necessary to make the feedback resistance (RFB) 10kΩ or over.
The use of the initial stage operational amplifier section allows configuration of a “Low band boost filter circuit”
described below.
This filter has a frequency response which is similar to the “Characteristics of low band boost filter” described
below, and the amount of boost (Gv) for the gain of initial stage inversion operational amplifier, and the cut-off
frequency (fb) at a point where the boost gain is reduced by 3dB can be described by the following formula.
CFB
CB
22pF
RFB
CI
RI
39kΩ
Lch(Rch)
RB
10μF 8.2kΩ
Low band boost filter circuit
NFINL(NFINR)
INL(INR)
Gain(dB)
Gainof
Gv
firststage
operational
amplifier
(RFB/RI)
fb
Characteristicsoflowbandboostfilter
-3dB
Frequency(Hz)
Gv(dB) = 20*log((RFB + RB)/RFB )
fb(Hz) = 1/(2π*CB*RB)
When low band boost function is used, the total gain in the low band that is boosted after it is amplified by the
digital amplifier section becomes “total gain (Av) + boost amount (Gv)".
For the "Example of application circuit", a capacitor (CFB) for cutting off high frequency range is attached for
limiting the band of input signal. The value can be adjusted if necessary. (Cut-off frequency = 1/(2π*CFB*RFB)).
DC cutting capacitor (CI) is attached for limiting the input DC current. This capacitor and input resistor (RI)
constitutes a low cutoff filter. Set the filter for sufficiently low cutoff frequency. (Cut-off frequency = 1/(2π*CI*RI)).
The external feedback resistors (RNFH and RNFL) are set so that they meet the following relational expression
depending on the input stage power supply voltage (VDD) and output stage power supply voltage (PVDD). For
RNFL, select the largest value resistor meeting this expression.
Use the resistor with an accuracy of 1for reduction of offset voltage.
RNFL≦VDD/(VDDP-VDD)*RNFH
600Ω≦(RNFH+RNFL)≦6kΩ
9
 

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