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11 | Keysight | Photodiode Test Using the Keysight B2980A Series - Technical Overview
L-I-V Test Example
This section explains how to synchronize the B2980A Series with other instruments using
the example of a laser diode (LD) L-I-V sweep test using a photodiode (PD).
Test System
Figure 4 shows a system diagram example to evaluate the L-I-V characteristics of a LD
using the B2900 Precision Instrument Family. The Keysight B2911A Precision Source/
Measure Unit (SMU) is used to apply drive current to the LD and to measure the LD's
voltage. The B2911A can cover currents from 10 fA to 3 A (DC)/10.5 A (pulsed) and
voltages from 100 nV to 210 V. The SMU has the capability to source and measure both
positive and negative voltages and currents, so it can easily characterize the LD's DC
parameters. Since the currents supplied to the LD can be quite large, a 4-wire connec-
tion (remote sensing) configuration is commonly used.
The B2985A/87A's ammeter input terminal is connected to the PD's anode and the
B2985A/87A's voltage source high terminal is connected to the PD's cathode. Since the
ammeter's and voltage source's low terminals are connected internally to the circuit
common, the PD current can be measured by applying voltage to the PD from its voltage
source.
In order to synchronize the B2985A/87A with the B2911A during the LD current sweep
operation, a trigger signal is sent from the B2911A to the B2985A/87A. The N1294A-031
GPIO-BNC Trigger Adapter converts the B2911A's digital I/O output to BNC outputs.
The N1294A-031 allows you to synchronize the triggering of the two units using an
inexpensive coaxial cable.
Figure 4. System configuration to evaluate the L-I-V Characteristics of a laser diode
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