STK401-020 Sanyo Semicon Device, STK401-020 Datasheet - Page 4

• Manufacturer Part Number: STK401-020
• Description: AF Power Amplifier
• Manufacturer: Sanyo Semicon Device

Description of External Circuits
R3, 13, 4, 14
C1, 11
C2, 12
C3, 13
C5, 15
R1, 11
R2, 12
R5, 15
R6, 16
C6, 7
C8, 9
R8, 9
L1, 2
For input coupling capacitor. Used for DC current blocking. When capacitor reactance with low frequency is increased, the reactance
value should be reduced in order to reduce the output noise from the signal resistance dependent 1/f noise. In response to the popping
noise which occurs when the system power is turned on, C1 and C11 which determine the decay time constant on the input side are
increased while C3 and C13 on the NF side are decreased.
For input filter capacitor. Permits high-region noise reduction by utilizing filter constructed with R1 and R11.
For NF capacitor. This capacitor determines the decline of the cut-off frequency and is calculated according to the following equation.
f
For the purpose of achieving voltage gains prior to reduction, it is best that C3 and C13 are large. However, because the shock
noise which occurs when the system power is turned on tends to increase, values larger than those absolutely necessary should be
avoided.
For oscillation prevention capacitor. A Mylar capacitor with temperature and frequency features is recommended.
For oscillation prevention capacitor. To ensure safe IC functioning, the capacitor should be installed as close as possible to the IC
power pin to reduce power impedance. An electrolytic capacitor is good.
For decoupling capacitor. Reduces shock noise during power up using decay time constant circuits with R8 and R9 and eliminates
components such as ripples crossing over into the input side from the power line.
For input filter applied resistor.
For input bias resistor. The input pin is biased to zero potential. Input impedance is mostly decided with this resistance value.
For resistors to determine voltage gain (VG). We recommend a VG = 40 dB using R3 and R13 = 560Ω and R4 and R14 = 56Ω. VG
adjustments are best performed using R3 and R13. When using R4 and R14 for such purposes, R4 and R14 should be set to equal R2
and R12 in order to establish a stable VN balance.
For oscillation prevention resistor.
For oscillation prevention resistor. This resistor’s electrical output resides in the signal frequency and is calculated according to the
following formula.
P R6 (16) =
f = output signal frequency upper limit
For ripple filter applied resistor. PO max, ripple rejection and power-up shock noise are modified according to this value. Set the
electrical output of these resistors while keeping in mind the flow of peak current during recharging to C8 and C9 which function as pre-
drive TR control resistors during load shorts.
For oscillation prevention coil. Compensates phase dislocation caused by load capacitors and ensures stable oscillation.
L
=
2π X C3 (13) X R3 (13)
(
1/2π fC5 (15) + R6 (16)
1
V
CC
max/√2
)
2
R6 (16)
STK401-020
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