Bradley 233 - Page 16

3. 7. 6. 233 Termination and Load Capability
Because of the arguments of 3. 6. 5. the 233 has been designed especially for source
termination, and care has been taken to minimize reflections at the generator.
Loads of any magnitude, whether resistive, inductive or capacitive may be driven without
limitation.
A series tuned circuit can cause the output voltage of the pulse generator to over-swing by
up to 70% of amplitude in special circumstances. In these cases the output voltage must be
kept within ±10V using the amplitude or offset controls.
For loads returned to voltages other than earth potential, or for active loads, the only
limitation is again the need to keep the output voltage in the ±10V range. Within this range
the generator always acts as a true 50S2 source at the end of the 50fi cable.
3.7.7 lOV into 50R
When it is required to drive an external 50S2 load at more than 5V amplitude, the internal
5012 resistors may be switched out using printed circuit mounted toggle switches. To gain
access remove the screws at each side of the top cover and lift off the cover. Set the
switch levers towards the front panel to disconnect the internal loads.
3.7.8 20V from each Output, into lOOfi
By disconnecting the internal loads as in 3.7. 7 and using a 100S2 1 watt resistor at the end of
each output cable, up to 20V amplitude is obtainable. The offset control must be used to
keep the signal within the ±10V from earth.
With a 4ft. 5012 cable the risetime will deteriorate. There will be a fast step of 2/3
amplitude, followed after 20 nanoseconds by another step 2/3 of the remaining amplitude
and so on. Better edges will be obtained with 7512, or preferably 100J2 cables.
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