Keithley 2520, User Manual, Page: 84 / 329

5-2 Source-Measure Concepts Model 2520 User’s Manual
Pulse concepts
Overview
The Model 2520 laser diode current source can output either DC or pulse waveforms.
Maximum current is as follows:
• DC: 1A
• Pulse mode: 5A
In addition, the current source can be operated in either the fixed or sweep mode. In the
fixed mode, the source simply outputs the programmed DC level (DC mode), or pulses at
a fixed amplitude (pulse mode). In the sweep mode, the source DC or pulse amplitude can
be swept across a series of steps at given increments. In addition, you can design your own
sweep waveforms by using the custom (list) sweep mode. See
“Sweep waveforms,” page
5-8 , for more sweep information.
Delay-pulse cycle
Model 2520 laser diode current source and voltage measurements consist of a series of
delay-pulse cycles (
Figure 5-1 ). During each cycle, the following occurs:
1. Wait for the programmed delay period.
2. Output the programmed current pulse.
3. During the current pulse, the 10MHz A/D converter processes a number of raw
voltage and current samples.
4. After the pulse, the raw samples are processed by a DSP (Digital Signal Processor)
into one set of laser diode voltage and detector current readings.
5. Repeat the cycle.
Figure 5-1
Delay-pulse cycle
Trigger
Delay
10MHz A/D
Conversions
Pulse