The Tektronix Type 111 Pretrigger Pulse Generator produces two pulse signals, one to trigger an oscilloscope sweep and a main output pulse to stimulate the device under test.
The trigger pulse comes between 30 and 250 nanoseconds before the output pulse; this is controlled by a knob on the 111. This gives adequate time for the oscilloscope to start sweeping so that the leading edge of the input or output signals of the device under test can be viewed. The alternative is to have a delay line in the signal path, after the trigger pickoff, but delay lines degrade transient performance. Using a pretrigger eliminates the need for a delay line in the vertical signal path and therefore enables accurate high-speed measurements. For a stable display, low jitter of the delay between pretrigger and main pulse is essential.
|Pulse repetition rate||10 Hz to 100 kHz, or by external trigger|
|Rise time||<500 ps|
|Pre-trigger||30−250 ns variable with additional calibrated "+1 ns" switch, jitter ≤100 ps|
|Output amplitude||≥10 V (selectable polarity) into 50 Ω|
The main output pulse of the Type 111 is produced by an avalanche transistor.
The Auxiliary Equipment section in the Type N manual says the rise time is 300 ps. The 111 front panel and manual specify <500 ps.