ADC Module - Analog Input Channel

Offset Adjustment Configuration



The schematic of the Analog Input Channel Rev. B in the Offset Adjustment Configuration, is persented here: ADC_Preamp_RevB_Offset.pdf It is the same circuit as the one with no offset; only some resistor values have been changed.

As shown, the circuit provides an offset compensation of 1V for a differential input signal.

With resistors A18 = A82 = 100 Ohm, the first stage has a gain of two. The signal is attenuated then by the shaper, and then amplified again by 2 and offset by 1V. Overall, we'll get a full scale recording of 16,000LSB for a dfifferential input excursion of about 1.5V. The overall gain can be increased or decreased, by changing resistors A18 and A82.

Plot1. This plot presents an actual PMT pulse that is applied at the input of the circuit in a differential manner, similar to the signal generated by the new KOTO PMT Base. (Yellow and blue are the two inputs, and red is the difference.) This pulse was originally recorded with an TDS3054B oscilloscope from a CsI/PMT/Base assembly. The recording was then loaded into an AWG5012 waveform generator, and used as input for the 14-BIT ADC Module.

 

Plot 2. This plot presents the same pulse after the differential amplifier, but before the shaper (yellow), and after the shaper (blue):


Plot 3. This plot presents the corresponding digital VME recording:


 



 
For questions regarding this page contact Mircea Bogdan.
bogdan@edg.uchicago.edu
Revised: Oct. 8, 2008