Digitally-programmable-attenuator

  
The first stage is a simple buffer used to isolate the signal source from the attenuator stages to follow. Each of the subsequent stages is preceded by a voltage divider formed by two resistors and CMOS switch. Provided that the CMOS switch for each stage is closed, the drive signal will be attenuated according to the basic voltage divider relationship at each stage. In the event a switch is open, nearly all of the signal strength will be passed to the next stage through the 1-K!l resistor. The amplifiers act as buffers for divider networks and reduce the interaction between stages.
Digitally-programmable-attenuator - schematic

Eight levels of attenuation are possible with the circuit as illust..rated, but more stages could be added. Each divider network must be closely matched to the resistor ratios shown or the level of attenuation will not match the levels in the logic chart.




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