The process of conversion of binary data into the analog signal is crucial for the obtainable speed and amplitude. We use a 14-bit digital-to-analog converter DAC904U settling within 30 ns. The current output from the DAC is converted to a voltage by a fast operational amplifier OPA690. This signal is fed to a high-voltage amplifier PA98.
The DAC uses twelve bits (b11…0) out of sixteen data bits available, that gives 50 mV resolution of the pulse amplitude at the high voltage output. The sixteenth bit (b15) may be set via software and is provided as TTL-level output on the front panel. It may be used for other purposes, like controlling external devices.
Two isolated BNC contacts for high voltage (±100V) output are provided on the front panel of each module, since one usually connects both the load and the oscilloscope probe to the same signal. If the load is connected between two outputs (as in the case of a liquid crystal cell) one needs to monitor the difference between the two applied signals. For this purpose two summation modules are provided. The summation module has one inverting (-IN) and one non-inverting (+IN) inputs which can accommodate the ±100V signals from high-voltage outputs of the generator. The output of the summation module is low voltage in the range ±10V, low power and intended for oscilloscope only.