VCC LS2 SPEAKER Q3 NPN Vo single transistor amplifier for current D/A VCC LS3 SPEAKER Q6 NPN Vo R5 680~1K single transistor amplifier with shunt resister for current D/A VCC R6 10 R9 820 Q7 NPN C2 220u D1 1N4148 R7 1 C1 R10 100u 180K C3 SPEAKER D2 1 Vo 1N4148 104 R11 330 C4 R8 100p Q8 NPN LS4 Q9 PNP Tranistor amplifier for current D/A !"# $%&'()* VCC LS7 Vo SPEAKER R22 Sound Q10 NPN 2K R21 680 Mixer circuit for Voive (current D/A) and melody +, " BZ1 LS8 BZ2 SPEAKER PWM direct driver speaker VCC SPEAKER LS1 Q2 NPN Q1 NPN R1 470 R2 470 Q5 Q4 NPN R3 1.5K NPN R4 1.5K BZ1 BZ2 4 transistor amplifier circuit for PWM output VCC C10 R15 C5 0.1u 10u 10K R14 1K C8 102 R20 10K 3 7 2 + 4 8 R16 6 1 BZ1 U1 C11 LM386 220u C9 0.1u BZ2 C6 0.1u 10K R13 1K R12 C7 102 LS5 5 10 power amplifier interface for PWM SPEAKER