Waveforms Of 1-Bit Circuit - Sharp SD-AT1000H Service Manual

SD-AT1000H
2.00V/div 2.00V/div
AD IC Output
1
2
500 ns/div
Amplitude
from 0 to 5 V
2.00 V/div 2.00 V/div
3
AD IC NF IN
4
500 ns/div

WAVEFORMS OF 1-BIT CIRCUIT

+ Side
5 V
- Side
194.545465 µs
520 mV
194.545465 µs
-12.30 V
In partial pressure OUT, 4 to 7 V amplitude
of GND reference is observed.
In IC of 75 kohms, the reference is 2.5 V
because of VREF. Due to imaginary GND
of operational amplifier inside IC, the
waveform cannot be monitored.
This waveform is partial pressure OUT.
2.00 V/div
LEVEL SHIFT OUT
5
T
2
6
1
ZOOM UP
10.0 V/div
+ FETOUT
2
11
12
1
Waveforms before low-pass filters at both
ends of the speaker.
H-bridge may be considered as BTL.
However, here and at the gate drive, dead
time is not observed; since bootstrap
operates based on output, DEAD TIME
part is in floating condition. The waveform
on the HIGH side shows that only the
booted voltage lowers.
– 42 –
2.00 V/div
DEAD TIME
50.0 ns/div 0.0 s
Dead time is generated by level
shift input.
Leading edge is delayed at CR,
passing R at DI.
Set value: 20 - 25 nsec.
10.0 V/div
+ SIDE
- SIDE
194.545465 µs
500 ns/div
T
-12.30 V
2
T
1
-12.3 V