LA3160 データシートの表示（PDF） - SANYO -> Panasonic
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LA3160 Datasheet PDF : 7 Pages
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LA3161
NAB element and determination of gain
Since the DC feedback is provided by R1, R2 of NAB element, which brings about DC output potential at pins 3, 6, it
is impossible to change the value of R1, R2 of NAB element greatly. Therefore, when determining the gain, change
RNF with R1, R2, C1 (NAB element) kept constant.
(1) How to obtain RNF
Impedance Z of NAB element is
Z
=
1
1/R1+jωC1
+ R2
=
(R1+R2)
{
1+jωC1 {R1R2/ (R1+R2)}
1+jωC1R1
}
For a general negative feedback amplifier circuit, A=Ao/(1+Aoβ) applies, and Z=A · RNF is obtained under
conditions of Ao>>A, A>>1 (β=RNF/ (RNF+Z), Ao=open-loop gain, A=feedback gain).
Therefore, we can use an approximation of RNF=Z/A.
A= (VG for 1kHz) times, (Set R1, R2 at approximately 100kΩ)
Each time constant of NAB characteristic.
Tape speed
T1 C1, R1
T2 C1 (R1//R2)
9.5cm/s
3180µs
90µs
4.75cm/s
1590µs
120µs
(2) Examples of NAB Constants
(a) Tape speed : 9.5cm/s. (8 tracks)
VG : RNF (VG/f=1kHz)
VG
30
35
40
dB
RNF 180 100
56
Ω
(b) Tape speed : 4.75cm/s. (cassette)
VG : RNF
VG
30
35
40
dB
RNF 440 240 130
Ω
(c) Flat amplifier
VG : RNF
VG
30
35
40
dB
RNF 3.2
1.8
1
kΩ
No.573–4/7
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