Delay And Width Generators - HP 8082A Operating And Service Manual

INVERTED,
DELAY ED
PULSE INPUT
NORMAL
PULSE INPUT
OUTPUT
4 - 1 4 Four current sources (Q2,03,
provide current for the rate generator; two of these sour-
ces (Q3 and Q9) are inhibited by logic switches
Q4, Q5j when the repetition rate is set to the fastest ran-
ge (100 - 250 M/Hz). Thus on the fastest range if capacitor
of the Schmitt trigger is high. In this state current from
Schmitt trigger flows into current sink Q8. When the
charge on CX has reached the threshold level of the
Schmitt trigger, the output of the Schmitt trigger and
hence the level at A goes to a low level. Current from
now flows, via A back into the Schmitt trigger and
discharges into current sink QB.
This action produces a triangular waveform
at point E3 and a 50% duty cycle square wave at the
Schmitt trigger output when both current sources
lower repetition rate ranges, current sources Q3 and
and the extra capacitors (C2 - C5) are switched in. The
circuit action is the same; the extra capacitors are re-
quired to provide the longer charge/discharge times. The
repetition rate is adjusted within each range by the rate
vernier, which adjusts the current from both current
sources simultaneously.
4 - 1 6 The square wave output from the Schmitt
trigger is used to drive the transition detector stage.
Transition Detector
This circuit produces two outputs; a trigger
4 - 1 8
output and a pulse output for the delay generator. The
Q8 and Q9)
Figure 4-4. Transition Detector Pulse Output
negative 50% duty cycle square wave, and can be switched
to either > 500mV or > 1 V amplitude. The pulse output
is produced by inverting and delaying the pulse input
(delay produced by 2ns fixed delay
ting this waveform, together with the normal pulse input,
to an AND gate. The resultant waveform is as shown in
Figure 4-4. The pulse spikes produced are of constant
width regardless of repetition rate and are input to the
Delay Generator. In Square Wave mode the Transition
Detector has no effect on the signal, i.e. the square wave
passesstraight through.
Repetition Rate Vernier
The repetition rate vernier produces a variab-
4 - 2 0
le voltage (OV to 6.4V) into a differential'amplifier
The output of the differential amplifier drives a transistor
two negative current sources.
4-21

DELAY AND WIDTH GENERATORS

4 - 2 2 The output of the Transition Detector is in-
put to the Delay Generator integrated circuit (U2). The
purpose of this circuit is to produce an output that is
delayed on the input by the setting of the delay controls.
The pulse width and shape remain unchanged. In double
pulse mode, both the delayed and undelayed pulses are
into two parts for delaying signals with different periods
appropriate part.
4 - 2 3
Figure 4-5 is a simplified diagram of the
Deiav Generator and should
he r&mwi