Keithley 2520, Service Manual, Page: 80 / 137

4-8 Troubleshooting Model 2520 Pulsed Laser Diode Test System Service Manual
Figure 4-2
Analog circuitry block diagram
High
DAC
U54
Voltage
Clamp
U4, U6
U16,Q9
Output
Stage
Q10-Q12
Current
Amplifiers
U8, U18
PULSED OUT
Terminals
Laser Diode Current Source
Control Data
From MPU
DAC
U1
Amplifier
and
Current
Drive
U20
DETECTOR 1
Bias Terminal
Detector 1 Voltage Bias Source
Control Data
From MPU
DAC
U2
Amplifier
and
Current
Drive
U3
DETECTOR 2
Bias Terminal
Detector 2 Voltage Bias Source
Control Data
From MPU
A/D
Converter
U31
Buffer
and
Ranging
U12,U13
PULSED SENSE
Terminals
Laser Diode Voltage Measurement
Sample Data
to SRAM
and DSP
A/D
Converter
U43
I-V
Converter
and
Ranging
U7,U8
Q10,Q11
DETECTOR 1
Current Input
Terminal
Detector 1 Current Measurement
Sample Data
to SRAM
and DSP
A/D
Converter
U53
I-V
Converter
and
Ranging
U10,U17
Q15,Q16
DETECTOR 2
Current Input
Terminal
Detector 2 Current Measurement
Sample Data
to SRAM
and DSP
Low
DAC
U1
Pulse
High/Low
Switch
U5