Random Tail Pulse Generator BNC Model DB-2

The Model PB-5 replaces the BH-1. Along with a suite of features and modes, the PB-5 is widely respected for its 155 uV amplitude resolution


  • Count Rate 10 Hz - 1 MHz
  • Random or repetitive modes
  • Rise Time 100 ns - 20 µs
  • Decay Time Constant 5 µs
  • Output Voltage Transition Range
    Repetitive 0 - 10 V or 0 - 0.25 V
    Random 0 - 0.25 V
  • Amplitude Shift (of voltage transition) vs. Frequency 
    <+/- 0.05% from 10 Hz to 100 kHz
  • Output Polarity Positive or Negative
  • Temperature Coefficient of Amplitude: 
    < +/- 0.02% / oC

The Model DB-2 is a pulse generator which accurately simulates the random and pileup characteristics of pulses from a radiation detector. It provides pulses which are monoenergetic over a broad range of average count rates. Under high count rate conditions, the pulses will pileup. This characteristic is useful in determining pile-up or count-rate effects and in measuring the resolution of high count rate spectroscopy systems. 
Besides random pulses, the Model DB-2 also provides monoenergetic repetitive pulses. In this mode, the DB-2 is an excellent general purpose pulser. When the EXT REF input is used, the DB-2 provides sliding pulses to quickly check system or component linearity. Since the DB-2 is a random pulser, a general purpose pulser, and has sliding pulse capabilities, it is one of our most versatile models.


External Trigger: 1 V positive pulse triggers a pulse (single or double), with internal delay and width controls operative. 50 Ohms input impedance, +/- 5 V maximum input.

Drive: 1 V positive pulse generates an output pulse with a width equal to the width of the incoming pulse, internal delay and width controls are operative. 50 Ohms input impedance, +/- 5 V maximum input. 

Internal / External Reference: With Internal Reference, the output pulse amplitude is controlled only by the Amplitude and Normalize controls. With External Reference, an applied positive level controls the output pulse amplitude.

Input: +5 V max, 5 k input impedance. 


Output Amplitude:

Flat Top: 0.0 V to 2 V into 50 Ohms, 0.0 V to 4 V into high impedance, continuously adjustable with ten-turn potentiometer. 50 Ohm source impedance. 

Tail Pulse: 0.0 V to 1.5 V into 50 Ohms, 0.0 V to 3 V into high impedance, continuously adjustable with ten-turn potentiometer. 50 Ohm source impedance. 

Polarity: Simultaneous positive and negative pulses are available. 

Trigger Out: Positive 3 V pulse, 10 ns rise time, 50 Ohms output impedance. 



Amplitude Characteristics: Temperature stability: less than 1% variation from 0-50 °C. 

Duty cycle variations: Less than 1%up to 90% duty factor. 

Linearity: less than 1% integral nonlinearity. 

Power Requirements: +12V at 500 mA, -12V 400 mA, +6V at 80 mA, -6 V at 425 mA.



Single cycle: One pulse occurs each time the push button is depressed.

Normalize: Multi-turn potentiometer will vary the amplitude up to 50%.

Rise Time (10-90%):

Tail Pulse: 3 ns to 250 ns in six steps.

Flat Top: 4 ns to 250 ns in six steps.

Decay Time Constant (100-37%): 5 ns to 10 µs in eight steps.

Frequency: A: 10 Hz to 50 MHz, continuously adjustable with coarse and fine controls. B: External trigger, 0 Hz to 50 MHz

Delay: 10 ns - 10 ms, continuously adjustable with coarse and fine controls.

Width: 5 ns - 5 ms, continuously adjustable with coarse and fine controls.

Flat Top / Tail Pulse: Toggle switch selects the output pulse shape. The width controls are functional only in the flat top mode.

Single/Double Pulse: In the single-pulse mode, a single output pulse occurs which is delayed from the Trigger Out by an amount determined by the Delay controls.

In the double-pulse mode, two equal-width out pulses occur. The first pulse is simultaneous with the Trigger Out. Pulse separation set by delay controls.


Size: Triple width NIM module 4.05" wide x 8,70" high in accordance with TID-20893 (Rev. 3).

Weight: 4.5 lbs. (2 kg) net; 7lbs. (3.2 kg) shipping. 

The Model DB-2 is ideally suited for high count rate or long tail time conditions. In other tail pulse generators, the pulse amplitude decreases when pulses start to ride up on the tail of the previous pulse. In the DB-2 the step amplitude is independent of pulse spacing. There are two modes of operation: repetitive and random.
In the repetitive mode the maximum output amplitude is 10 V. This range is useful for connecting directly to a linear amplifier to test stability and linearity.
In the random mode, the maximum output amplitude is 1.0 V. This provides a large dynamic range, i.e., it allows for a larger number of pulses to pile up on the tails of each other without saturation. A typical application of the random pulse mode is to connect the output of the Model DB-2 to a test capacitor input of a preamplifier in a pulse height analyzer system. The count rate is set low, about 1 kHz and the pole-zero adjustment of the post-amplifier is made for minimum broadening of the line width on the analyzer. Then the count rate is increased until the broadening exceeds an acceptable value. 
The user then knows the highest permissible count rate with a live source. Other applications of the Model DB-2 include testing the counting loss of scalers and ratemeters under random conditions and proper adjustment of base line restorers. 
With each output pulse occurs a Trigger Out pulse, which will enable the user to separately count output pulses. Also, when the frequency switch is set for External Frequency, the timing and the number of output pulses will be controlled by the timing and number of pulses present at the External Trigger connector. 
Another useful application of the DB-2 is in the generation of sliding pulses. Sliding pulses result when the signal from a ramp generator, such as the BNC Model LG-1, is connected to the External Reference connector of the DB-2. (For sliding pulses the Reference toggle switch would be in the External position.) The resulting pulses, whose amplitudes linearly increase and decrease in time, can be connected to a multi-channel analyzer system to quickly and easily check the linearity of the system and its components. 
With the fast pulse repetition rates available, counts are quickly accumulated. For a linear MCA system, this results in an equal number of counts in all channels and hence a straight line in the counts versus channel number display.

We offer BNC pulse generators only if end users are in Europe, other customers please contact BNC directly.