The pipeline readout amplifier ("pipeamp")

The pipeline readout amplifier is a switched charge sensitive amplifier (fig. 6). Before operation the internal reset signal is applied thus discharging the two capacitances (for clearness assume Vdcl= Vd). After the reset the pipeamp is sensitive to the pipeline capacitor charge; since the node at the inverting input stays on constant potential, the charge transfer between the two capacitors causes a related voltage on the output when coupling charge to the input.

  

Figure 6: Pipeline readout amplifier: a switched charge sensitive amplifier

The following strategy is recommended in case of radiation damage:

• Vd controls the reset level; it should follow the frontend baseline shift, i. e. it should be countinously diminished.
• Vdcl controls the folded cascode "ground" level; it should be adjusted after the Vd adjustment such that the channel output offsets equal aproximately the pipeline column number's mean value in the readout figure.
• Ipipe sets the pipeamp bias current. It should be kept constant.