Saturday, 24 March 2012

the Block diagram of a general purpose oscilloscope and its Basic operation

Block diagram of a general purpose oscilloscope:

the basic block diagram of a general purpose oscilloscope.
A general purpose oscilloscope consists of following parts.
1. Cathode ray tube                                                                        

2. Vertical amplifier

3. Delay line

4. Time base circuit

5. Horizontal amplifier

6. Trigger circuit

7. Power supply.

1. Cathode Ray Tube:
Cathode Ray Tube is the heart of the oscilloscope. When the electrons emitted by the electron gun strikes the
phosphor screen of the CRT, a visual signal is displayed on the CRT.

2. Vertical Amplifier
In Vertical Amplifier,The input signals are amplified by the vertical amplifier. Usually, the vertical amplifier is a wide
band amplifier which passes the entire band of frequencies.

3. Delay Line
Delay Line as the name suggests that, this circuit is used to, delay the signal for a period of time in the vertical section of CRT. The input signal is not applied directly to the vertical plates because the
part of the signal gets lost, when the delay Time not used. Therefore, the input signal is delayed
by a period of time.

4. Time Base Circuit
Time base circuit uses a uni junction transistor, which is used to produce the sweep. The saw
tooth voltage produced by the time base circuit is required to deflect the beam in the horizontal
section. The spot is deflected by the saw tooth voltage at a constant time dependent rate.

5. Horizontal Amplifier
In Horizontal Amplifier,The saw tooth voltage produce by the time base circuit is amplified by the horizontal amplifier before it is applied to horizontal deflection plates

6. Trigger Circuit
In theTrigger Circuit The signals which are used to activate the trigger circuit are converted to trigger pulses for the
precision sweep operation whose amplitude is uniform. Hence input signal and the sweep
frequency can be synchronized.

7. Power supply:
The Power supply voltages require by CRT, horizontal amplifier and vertical amplifier are provided by the power supply block.

 Power supply block of oscilloscope is classified in to two types
(1) Negative high voltage supply
(2) Positive low voltage supply
The voltages of negative high voltage supply is from -1000V to -1500V and the range of positive
voltage supply is from 300V to 400V approx.


  1. Why two ranges of supply is used in CRO???
    Need some basic description
    1 . tooth voltage
    2.tigger pulse.

  2. This comment has been removed by the author.

  3. Thank you so much sir, neatly explained