Avtech 14258, Инструкция по эксплуатации

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TIMING CONTROL
BASIC TIMING CONTROL
This instrument can be triggered by its own internal clock or by an external TTL trigger
signal. In either case, two output channels respond to the trigger: PULSE and SYNC.
The PULSE output is a bipolar signal that may either drive a 50 Ohm load, or the test jig
described later. The positive and negative amplitudes are adjustable. The pulse widths
and delays are not adjustable.
The SYNC pulse is a fixed-width TTL-level reference pulse used to trigger oscilloscopes
or other measurement systems.
These pulses are illustrated below, assuming internal triggering:
The forward-bias pulse (V
1
) is approximately 100 us wide, and has a slow rise time
(governed by the R
1
× C
2
time constant – see equivalent circuit in the “BASIC
AMPLITUDE CONTROL” section for for details about R
1
and C
2
.)
After 80 us, V
1
has reached a stable voltage, and the SYNC output pulse is generated
(to allow triggering of oscilloscopes). Shortly after the end of the SYNC pulse, the
negative pulse (V
2
) is triggered, and is coupled onto the output signal. The negative
pulse lasts 2 us, approximately. (V
2
droops slightly during the 2 us time, since it is
capacitively coupled to the output. However, this droop can generally be ignored.) The
DUT reverse recovery transient will occur within this 2 us time. After the end of the V
2
pulse, the waveform will complete the forward-bias pulse, but this occurs after the
recovery waveform of interest has been obtained.
20
SYNC OUT
(generated by the
internal oscillator)
SMALL PROPAGATION DELAY (~ 200 ns)
Mainframe OUT
With DUT = 0 Ohms
80 us
3V, FIXED
V1 (+),
VARIABLE
V2 (-),
VARIABLE
100 us
2 us
NOT TO SCALE
CURRENT
THROUGH DIODE
(DASHED LINE)
t
RR