* SPICE netlist
R1 N001 Vin_audio {R1a}
R2 N001 0 {R3a}
C1 N001 N007 {Ca}
C2 N001 Vout_BPF1 {Ca}
R3 Vout_BPF1 N007 {R2a}
XU1 Vcom N007 Vdd 0 Vout_BPF1 level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
V1 Vdd 0 5
R4 Vcom Vdd 5k
R5 0 Vcom 5k
R6 N016 Vin_audio {R1b}
R7 N016 0 {R3b}
C3 N016 N022 {Cb}
C4 N016 Vout_BPF2 {Cb}
R8 Vout_BPF2 N022 {R2b}
XU2 Vcom N022 Vdd 0 Vout_BPF2 level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
V2 Vin_audio 0 SINE(2.5 1 520) AC 1
XU3 Vcom N014 Vdd 0 Ain level2 Avol=1Meg GBW=10Meg Slew=10Meg Ilimit=25m Rail=0 Vos=0 En=0 Enk=0 In=0 Ink=0 Rin=500Meg ;pnba In+)In-)V+)V-)OUT
R9 Ain N014 {R}
R10 N014 Vout_BPF1 {R}
R11 N014 Vout_BPF2 {R}
XU4 Vcom N008 Vdd 0 Vramp_class-d AD8648 ;pnba In+)In-)V+)V-)OUT
R12 N008 N002 27.05k
R13 N010 Vramp_class-d 9.81k
R14 N002 N010 53.4k
C5 Vramp_class-d N008 10n
R15 N002 Vdd 1k
C6 Vin_a+ Ain 4.7
R16 N005 Vin_a+ 100k
XU6 Vcom N005 Vdd 0 Vin_a- AD8648 ;pnba In+)In-)V+)V-)OUT
R17 Vin_a- N005 100k
R18 V_pwm-p Vdd 1k
R19 V_pwm-n Vdd 1k
A1 N003 0 0 0 0 P001 0 0 BUF VHigh=5
A2 P001 0 0 0 0 N004 0 0 BUF VHigh=5
A3 N009 0 0 0 0 N012 0 0 BUF VHigh=5
A4 N017 0 0 0 0 N018 0 0 BUF VHigh=5
A5 N018 0 0 0 0 P002 0 0 BUF VHigh=5
A6 N021 0 0 0 0 N023 0 0 BUF VHigh=5
Q1 N006 N004 Vdd 0 2N2907
Q2 N020 P002 Vdd 0 2N2907
Q3 N006 N012 0 0 2N2222
Q4 N020 N023 0 0 2N2222
R20 N011 N013 16
R21 N015 N019 16
L1 N013 N015 1000
C7 0 N003 10n
C8 N009 0 100n
C9 0 N017 10n
C10 N021 0 100n
E1 N011 N019 N006 N020 1
.tran 200ms
.param R1a=100k R2a=200k R3a=500 Ca=100n R1b=25k R2b=50k R3b=132 Cb=100n R=1k

* LTspice schematic (.asc)
Version 4.1
SHEET 1 5904 848
WIRE -2264 -392 -2328 -392
WIRE -2040 -392 -2200 -392
WIRE -360 -360 -952 -360
WIRE 2296 -360 2264 -360
WIRE 2472 -360 2424 -360
WIRE 2264 -328 2264 -360
WIRE 2264 -328 2248 -328
WIRE 488 -312 456 -312
WIRE 648 -312 568 -312
WIRE 2136 -312 2088 -312
WIRE 2776 -312 2536 -312
WIRE -2168 -296 -2200 -296
WIRE -2040 -296 -2040 -392
WIRE -2040 -296 -2088 -296
WIRE -792 -296 -840 -296
WIRE -680 -296 -728 -296
WIRE 2264 -296 2248 -296
WIRE -488 -280 -520 -280
WIRE -360 -280 -360 -360
WIRE -360 -280 -408 -280
WIRE 2952 -280 2824 -280
WIRE 2264 -264 2264 -296
WIRE 2328 -264 2264 -264
WIRE 2472 -264 2392 -264
WIRE -2856 -248 -2952 -248
WIRE 1112 -232 1064 -232
WIRE 1112 -200 1064 -200
WIRE 1400 -200 1112 -200
WIRE -952 -184 -952 -360
WIRE -840 -184 -840 -296
WIRE -840 -184 -872 -184
WIRE -792 -184 -840 -184
WIRE -2856 -168 -2952 -168
WIRE -2456 -168 -2552 -168
WIRE -2328 -168 -2328 -392
WIRE -2328 -168 -2376 -168
WIRE -2296 -168 -2328 -168
WIRE -2200 -168 -2200 -296
WIRE -2200 -168 -2232 -168
WIRE -2152 -168 -2200 -168
WIRE -680 -168 -680 -296
WIRE -680 -168 -728 -168
WIRE -632 -168 -680 -168
WIRE -520 -168 -520 -280
WIRE -520 -168 -552 -168
WIRE -488 -168 -520 -168
WIRE 248 -168 88 -168
WIRE 328 -168 312 -168
WIRE 344 -168 328 -168
WIRE 456 -168 456 -312
WIRE 456 -168 424 -168
WIRE 488 -168 456 -168
WIRE 2824 -168 2824 -280
WIRE -2040 -152 -2040 -296
WIRE -2040 -152 -2088 -152
WIRE -1960 -152 -2040 -152
WIRE -392 -152 -424 -152
WIRE 648 -152 648 -312
WIRE 648 -152 552 -152
WIRE 664 -152 648 -152
WIRE 2776 -152 2776 -312
WIRE 2952 -152 2952 -200
WIRE -360 -120 -360 -280
WIRE -360 -120 -424 -120
WIRE -2328 -104 -2328 -168
WIRE -1528 -104 -1560 -104
WIRE -1400 -104 -1448 -104
WIRE 2952 -24 2952 -72
WIRE -1720 -8 -1768 -8
WIRE -1608 -8 -1640 -8
WIRE -680 8 -680 -168
WIRE 1112 8 1064 8
WIRE -2552 24 -2552 -168
WIRE -2552 24 -2568 24
WIRE -1608 24 -1608 -8
WIRE -1560 24 -1560 -104
WIRE -1560 24 -1608 24
WIRE -1528 24 -1560 24
WIRE 328 24 328 -168
WIRE 664 24 328 24
WIRE -1400 40 -1400 -104
WIRE -1400 40 -1464 40
WIRE -1304 40 -1400 40
WIRE 1112 40 1064 40
WIRE 1400 40 1112 40
WIRE -2264 56 -2328 56
WIRE -2040 56 -2200 56
WIRE 2296 56 2264 56
WIRE 2408 56 2360 56
WIRE 2824 56 2824 -88
WIRE 2952 56 2824 56
WIRE -1720 72 -1768 72
WIRE -1608 72 -1608 24
WIRE -1608 72 -1640 72
WIRE 2264 88 2264 56
WIRE 2264 88 2248 88
WIRE 2136 104 2088 104
WIRE 2776 104 2776 -104
WIRE 2776 104 2536 104
WIRE 2264 120 2248 120
WIRE -2168 152 -2200 152
WIRE -2040 152 -2040 56
WIRE -2040 152 -2088 152
WIRE 2264 152 2264 120
WIRE 2328 152 2264 152
WIRE 2472 152 2392 152
WIRE -2552 280 -2552 24
WIRE -2456 280 -2552 280
WIRE -2328 280 -2328 56
WIRE -2328 280 -2376 280
WIRE -2296 280 -2328 280
WIRE -2200 280 -2200 152
WIRE -2200 280 -2232 280
WIRE -2152 280 -2200 280
WIRE -2040 296 -2040 152
WIRE -2040 296 -2088 296
WIRE -1960 296 -2040 296
WIRE -2328 344 -2328 280
FLAG -2120 -120 0
FLAG -2328 -24 0
FLAG -2856 -88 0
FLAG -2856 -328 0
FLAG -2120 328 0
FLAG -2328 424 0
FLAG -1960 -152 Vout_BPF1
IOPIN -1136 -896 Out
FLAG -1960 296 Vout_BPF2
IOPIN -1136 -448 Out
FLAG -2568 24 Vin_audio
IOPIN -1744 -720 In
FLAG -2952 -248 Vcom
FLAG -2152 -136 Vcom
FLAG -2152 312 Vcom
FLAG -2952 -168 Vdd
FLAG -2120 264 Vdd
FLAG -2120 -184 Vdd
FLAG -2920 216 0
FLAG -2920 136 Vin_audio
IOPIN -2096 -608 Out
FLAG -1768 -8 Vout_BPF1
IOPIN -944 -752 In
FLAG -1768 72 Vout_BPF2
IOPIN -944 -672 In
FLAG -1496 8 Vdd
FLAG -1496 72 0
FLAG -1528 56 Vcom
FLAG -760 -136 0
FLAG -392 -152 0
FLAG -760 -200 Vdd
FLAG -424 -184 Vdd
FLAG -792 -152 Vcom
FLAG -488 -136 Vcom
FLAG -360 -40 Vdd
FLAG -680 8 Vramp_class-d
IOPIN 144 -736 Out
FLAG 488 -136 Vcom
FLAG 520 -120 0
FLAG 520 -184 Vdd
FLAG 664 -152 Vin_a-
FLAG 664 24 Vin_a+
FLAG 88 -168 Ain
IOPIN 912 -912 In
FLAG 1000 -248 Vin_a+
FLAG 1000 -8 Vin_a-
FLAG 1064 -264 Vdd
FLAG 1064 -24 Vdd
FLAG 1112 -232 0
FLAG 1112 8 0
FLAG 1112 -120 Vdd
FLAG 1112 120 Vdd
FLAG 1400 -200 V_pwm-p
IOPIN 2224 -944 Out
FLAG 1400 40 V_pwm-n
IOPIN 2224 -704 Out
FLAG 1000 -216 Vramp_class-d
IOPIN 1824 -960 In
FLAG 1000 24 Vramp_class-d
IOPIN 1824 -720 In
FLAG 2536 -408 Vdd
FLAG 2536 8 Vdd
FLAG 2536 -216 0
FLAG 2536 200 0
FLAG 2264 -424 0
FLAG 2264 -200 0
FLAG 2264 -8 0
FLAG 2264 216 0
FLAG 2088 -312 V_pwm-p
IOPIN 2912 -1056 In
FLAG 2088 104 V_pwm-n
IOPIN 2912 -640 In
FLAG -1304 40 Ain
IOPIN -480 -704 Out
SYMBOL res -2360 -184 R90
SYMATTR InstName R1
SYMATTR Value {R1a}
SYMBOL res -2344 -120 R0
SYMATTR InstName R2
SYMATTR Value {R3a}
SYMBOL cap -2296 -184 M90
SYMATTR InstName C1
SYMATTR Value {Ca}
SYMBOL cap -2264 -408 M90
SYMATTR InstName C2
SYMATTR Value {Ca}
SYMBOL res -2072 -312 R90
SYMATTR InstName R3
SYMATTR Value {R2a}
SYMBOL OpAmps\\UniversalOpAmp2 -2120 -152 R0
SYMATTR InstName U1
SYMBOL voltage -2856 -184 R0
SYMATTR InstName V1
SYMATTR Value 5
SYMBOL res -2872 -264 R0
SYMATTR InstName R4
SYMATTR Value 5k
SYMBOL res -2872 -344 R0
SYMATTR InstName R5
SYMATTR Value 5k
SYMBOL res -2360 264 R90
SYMATTR InstName R6
SYMATTR Value {R1b}
SYMBOL res -2344 328 R0
SYMATTR InstName R7
SYMATTR Value {R3b}
SYMBOL cap -2296 264 M90
SYMATTR InstName C3
SYMATTR Value {Cb}
SYMBOL cap -2264 40 M90
SYMATTR InstName C4
SYMATTR Value {Cb}
SYMBOL res -2072 136 R90
SYMATTR InstName R8
SYMATTR Value {R2b}
SYMBOL OpAmps\\UniversalOpAmp2 -2120 296 R0
SYMATTR InstName U2
SYMBOL voltage -2920 120 R0
SYMATTR Value2 AC 1
SYMATTR InstName V2
SYMATTR Value SINE(2.5 1 520)
SYMBOL OpAmps\\UniversalOpAmp2 -1496 40 R0
SYMATTR InstName U3
SYMBOL res -1432 -120 R90
SYMATTR InstName R9
SYMATTR Value {R}
SYMBOL res -1624 -24 R90
SYMATTR InstName R10
SYMATTR Value {R}
SYMBOL res -1624 56 R90
SYMATTR InstName R11
SYMATTR Value {R}
SYMBOL OpAmps\\AD8648 -760 -232 R0
SYMATTR InstName U4
SYMBOL res -856 -200 R90
SYMATTR InstName R12
SYMATTR Value 27.05k
SYMBOL res -536 -184 R90
SYMATTR InstName R13
SYMATTR Value 9.81k
SYMBOL res -392 -296 R90
SYMATTR InstName R14
SYMATTR Value 53.4k
SYMBOL cap -728 -312 R90
SYMATTR InstName C5
SYMATTR Value 10n
SYMBOL res -376 -136 R0
SYMATTR InstName R15
SYMATTR Value 1k
SYMBOL cap 312 -184 R90
SYMATTR InstName C6
SYMATTR Value 4.7�
SYMBOL res 440 -184 R90
SYMATTR InstName R16
SYMATTR Value 100k
SYMBOL OpAmps\\AD8648 520 -216 R0
SYMATTR InstName U6
SYMBOL res 584 -328 R90
SYMATTR InstName R17
SYMATTR Value 100k
SYMBOL res 1096 -216 R0
SYMATTR InstName R18
SYMATTR Value 1k
SYMBOL res 1096 24 R0
SYMATTR InstName R19
SYMATTR Value 1k
SYMBOL Digital\\inv 2296 -424 R0
SYMATTR Value2 VHigh=5
SYMATTR InstName A1
SYMBOL Digital\\inv 2360 -424 R0
SYMATTR Value2 VHigh=5
SYMATTR InstName A2
SYMBOL Digital\\inv 2328 -328 R0
SYMATTR Value2 VHigh=5
SYMATTR InstName A3
SYMBOL Digital\\inv 2296 -8 R0
SYMATTR Value2 VHigh=5
SYMATTR InstName A4
SYMBOL Digital\\inv 2408 -8 R0
SYMATTR Value2 VHigh=5
SYMATTR InstName A5
SYMBOL Digital\\inv 2328 88 R0
SYMATTR Value2 VHigh=5
SYMATTR InstName A6
SYMBOL pnp 2472 -312 M180
SYMATTR InstName Q1
SYMATTR Value 2N2907
SYMBOL pnp 2472 104 M180
SYMATTR InstName Q2
SYMATTR Value 2N2907
SYMBOL npn 2472 -312 R0
SYMATTR InstName Q3
SYMATTR Value 2N2222
SYMBOL npn 2472 104 R0
SYMATTR InstName Q4
SYMATTR Value 2N2222
SYMBOL res 2936 -296 R0
SYMATTR InstName R20
SYMATTR Value 16
SYMBOL res 2936 -40 R0
SYMATTR InstName R21
SYMATTR Value 16
SYMBOL ind 2936 -168 R0
SYMATTR InstName L1
SYMATTR Value 1000�
SYMBOL cap 2248 -424 R0
SYMATTR InstName C7
SYMATTR Value 10n
SYMBOL cap 2248 -264 R0
SYMATTR InstName C8
SYMATTR Value 100n
SYMBOL cap 2248 -8 R0
SYMATTR InstName C9
SYMATTR Value 10n
SYMBOL cap 2248 152 R0
SYMATTR InstName C10
SYMATTR Value 100n
SYMBOL e 2824 -184 R0
SYMATTR InstName E1
SYMATTR Value 1