152
4000 X-Series Oscilloscopes Advanced Training Guide
A
Oscilloscope Block Diagram and Theory of Operation
DSO Block Diagram
shows the block diagram of one channel of acquisition of a typical
digital storage oscilloscope (DSO). The yellow-shaded blocks represent system
components unique to a single channel of acquisition, such as Channel-1 or
Channel-2. The blue-shaded blocks represent system components that are
common among all channels of acquisition, such as the scope’s common timebase
and CPU system.
ADC Block
Shown near the middle of this block diagram is the analog-to-digital convertor
(ADC). The ADC block is the core/central component of all DSOs. The function of
this block is to convert the analog input into a series of digital words. Most of
today’s DSOs utilize 8-bit ADCs which will provide 256 unique digital output
levels/codes. These digital binary codes are stored in the scope’s acquisition
memory, which will be discussed later. If the analog input level to the ADC is equal
to or less than –V, then the output of the ADC will be 00000000 (0 decimal). If the
analog input level to the ADC is equal to or greater than +V, then the output of the
ADC will be 11111111 (255 decimal). If the analog input level to the ADC is equal
to 0.0 V, then the output of the ADC will be 10000000 (128 decimal).
Figure 103
DSO block diagram
Attenuator
Amplifier
8-bit
ADC
Display
DSP
Scope Display
Acquistion
Memory
CPU
System
Timebase
System
Trigger
Logic
Trigger
Coupling
Trig Comp
Input
BNC
DC
Offset
DC Trigger
Level
