2
3 Technical data
Filament voltage:
≤
7.5 V
Filament current:
≤
3 A approx.
Anode voltage:
max. 500 V
Anode current:
2.5 mA typical
at
U
A
= 300 V,
U
F
= 6.3 V
DC
Length of tube:
300 mm approx.
Diameter:
130 mm approx.
Distance between
cathode and anode:
15 mm approx.
4. Operation
To perform experiments using the diode, the follow-
ing equipment is additionally required:
1 Tube holder D
U19100
1 DC power supply 0 – 500 V
U33000-115
or
1 DC power supply 0 – 500 V
U33000-230
4.1 Setting up the tube in the tube holder
•
The tube should not be mounted or removed
unless all power supplies are disconnected.
•
Push the jaw clamp sliders on the stanchion of
the tube holder right back so that the jaws
open.
•
Push the bosses of the tube into the jaws.
•
Push the jaw clamps forward on the stanchions
to secure the tube within the jaws.
4.2 Removing the tube from the tube holder
•
To remove the tube, push the jaw clamps right
back again and take the tube out of the jaws.
5. Sample experiments
5.1 Generation of charge carriers by a hot cath-
ode (thermionic effect) and measurement of
the anode current in dependency on the
power supplied to the cathode filament
Additionally required:
1 Analogue multimeter AM50
U17450
•
Set up the circuit as in Fig. 1. Connect the mi-
nus-pole of the anode voltage to the 4-mm
socket marked with a minus.
•
Start with the filament cold (filament voltage
U
F
= 0).
•
Vary the anode voltage
U
A
between 0 and 300 V.
Practically no current (< 0.1 µA) flows between the
cathode filament and the anode, even at high volt-
ages.
•
Apply 6 V to the filament so that it gets hot,
gradually increase the anode voltage and meas-
ure the anode current
I
A
.
•
Set the filament voltage back to zero, let it cool,
then gradually increase the filament voltage
with a fixed anode voltage and observe the ef-
fect on the anode current.
When the filament voltage is fixed, the anode cur-
rent increases in proportion to the anode voltage.
With the anode voltage fixed, the anode current
increases in proportion to the filament voltage.
5.2 Recording diode characteristics
•
Set up the circuit as in Fig. 1. Connect the mi-
nus-pole of the anode voltage to the 4-mm
socket marked with a minus.
•
Set filament voltages of 4.5 V, 5 V and
6 V.
•
Determine how the anode current
I
A
depends on
the anode voltage
U
A
for each of the filament
voltages by raising the anode voltage step by
step from 40 V to 300 V.
•
Plot the values of
I
A
and
U
A
on a graph.
With increasing the anode voltage the anode current
rises to an approximately steady value known as the
saturation current.
With increasing the filament voltage the anode
current rises.
5.3 Diode rectifier
Additionally required:
1 10 k
Ω
resistor
1 power supply for 16 V AC
1 oscilloscope
•
Set up the circuit as in Fig. 3 with
U
F
= 6.3 V and
U
A
= 16 V AC
•
Using an oscilloscope to measure the voltage
across the 10 k
Ω
resistor, observe the rectifier
operation of the diode
When the anode circuit operates as a diode, an AC
voltage is rectified in that during one half of the
current waveform the current is prevented from
flowing.
