Datasheet LA4555 (Sanyo) - 4

制造商Sanyo
描述2-Channel AF Power Amplifier for Radio, Tape Recorder Use
页数 / 页10 / 4 — LA4555. Application Circuits
文件格式/大小PDF / 354 Kb
文件语言英语

LA4555. Application Circuits

LA4555 Application Circuits

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文件文字版本

LA4555
Continued from preceding page. C7 (C8) : Output capacitor. The low cutoff frequency is determined by the following formula. 1 fL : Low cutoff frequency fL= 2πC7RL RL : Load resistance To make the low frequency response in the bridge amplifier mode identical with that in the stereo mode, the capacitor value must be doubled. C9 : Decoupling capacitor. Used for the ripple filter. Since the rejection effect is saturated at a certain capacitor value, it is meaningless to increase the capacitor value more than needed. This capacitor, being also used for the time constant of the muting circuit, affects the starting time. C10 : Power source capacitor.
Application Circuits
Voltage gain adjust · Stereo mode The voltage gain is determined by on-chip resistor R1 (R2) and external feedback resistor Rf as follows : R1 VG=20 log [dB] Rf1+R2 Any voltage gain can be obtained by external resistor Rf. · Bridge amplifier 1 mode Since point A is at the same potential as Vi and point B is a virtual GND point, R1 Vo1≈ Vi R2+R4+Rf1+Rf2 –R3 Vo2≈ Vi R2+R4+Rf1+Rf2 R1+R3 Vo = Vo1 – Vo2 = Vi R2+R4+Rf1+Rf2 Vo R1+R3 VG=20 log =20log [dB] Vi R2+R4+Rf1+Rf2 Assuming R2=R4=50Ω, R1=R3=20kΩ and Rf1=Rf2, the voltage gain is obtained by : R1 VG=20 log [dB] Rf1+R2 · Bridge amplifier 2 mode The CH1 is a noninverting amplifer and the CH2 is an inverting amplifier. The total voltage gain, being apparently higher than that of the CH1 by 6dB, is approximately calculated by the following formula. VG=20log R2/R1+6 (dB) To reduce the voltage gain, Rf is connected and the following formula is used. VG=20log R2/Rf+R1+6 (dB) No.1697–4/10