Theory of Operation
Analog Section Detailed Circuit Description 2
2-143
connector is connected back to the OUTPUT HI SENSE and OUTPUT LO SENSE
binding posts.
Attenuation is calibrated starting with 70 dB and decreased in 10 dB steps to 0 dB. The
Switch Matrix assembly connects the output of the Wideband AC module to its internal
cal zero amplifier circuit during all attenuator calibrations except the 0 dB and 10 dB.
The internal cal zero amplifier circuit provides a gain of 10 to Wideband output during 20
dB to 70 dB attenuation calibration. The output of this amplifier is connected to the RCL
line which is routed to the +input of the adc circuit on the DAC assembly. Output from
the DAC is connected to the -input of the adc circuit and adjusted until a null is achieved.
The exact attenuator value is then determined.
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