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4.6 OUTPUT VOLTAGE LEVEL PROGRAMMING
Two 12 bit digital to analog converters (DAC's) provide the output switch reference voltages.
The DAC's have built in safety features to prevent damage if the positive reference is programmed
below t he nega tive volt age; how ever, t he user should try to prevent this situat ion. The output
logic switches the high and low r eference voltag es into a p ower op-amp output stage. The pulse
string from the pulse generation logic provides t he contr ol to the switch, while the reference
voltages pr ovide the vo ltage levels. The op-amp power stage has 2-3 ohms output impedance. A
jumper select able r esistor betw een the o p-amp output and the BNC provides isolation and back
termination. The resulting output impedance is about 5 ohms with jumper J5 installed and 50
ohms with Jumper J6 installed. A load of 50 ohms or more is recommended.