STK4172II

No. 2323—6/8

Description of External Parts

C1, C2

Input filter capacitors

• A filter formed with R3 or R4 can be used to reduce noise at high frequencies.

C3, C4

Input coupling capacitors

• Used to block DC current. When the reactance of the capacitor increases at low frequencies, the dependence of 1/f noise on signal source

resistance causes the output noise to worsen. It is better to decrease the reactance.

• To reduce the pop noise at the time of application of power, it is effective to increase C3, C4 that fix the time constant on the input side and

to decrease C5, C6 on the NF side.

C5, C6

NF capacitors

• These capacitors fix the low cutoff frequency as shown below.

To provide the desired voltage gain at low frequencies, it is better to increase C5. However, do not increase C5 more than needed because

the pop noise level becomes higher at the time of application of power.

C15

Decoupling capacitor

C11, C12

Bootstrap capacitors

• When the capacitor value is decreased, the distortion is liable to be higher at low frequencies.

C9, C10

Oscillation blocking capacitors

• Must be inserted as close to the IC power supply pins as possible so that the power supply impedance is decreased to operate the IC stably.

• Electrolytic capacitors are recommended for C9, C10.

C14

Capacitor for ripple filter

• Capacitor for the TR10-used ripple filter in the IC system

C7

Oscillation blocking capacitor

• A polyester film capacitor, being excellent in temperature characteristic, frequency characteristic, is recommended for C7.

R3, R4

Resistors for input filter

R1, R2

Input bias resistors

• Used to bias the input pin potential to zero. These resistors fix the input impedance practically.

R5, R9

(R6, R10)

These resistors fix voltage gain VG.

It is recommended to use R5 (R6) = 560

Ω, R9 (R10) = 56kΩ for VG = 40dB.

• To adjust VG, it is desirable to change R5 (or R6).

R11, R13

(R12, R14)

Bootstrap resistors

• The quiescent current is set by these resistors 3.3k

Ω + 3.3kΩ. It is recommended to use this resistor value.

R21

Resistor for ripple filter

• (Limiting resistor for predriver transistor at the time of load short)

R18

Used to ensure plus/minus balance at the time of clip.

R19, R20

Resistor for ripple filter

allowing for the power that may be dissipated on that occasion.

R15, R16

Oscillation blocking resistors

f

L

1

2

π C5 R5

⋅⋅

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=

[Hz]