Pixelman Settings

Please follow the convention started, using the 'definition list' in alphabetic order, and define the settings.

Pixelman device DAC settings definitions:

Bias: A voltage or current that sets a steady operating condition for a circuit such as a transistor amplifier, or for a diode. The value of the bias is selected to provide optimum performance of the circuit. [2]




Disc: A current reference.

FBK: FBK is a voltage reference. FBK sets the idle voltage level of the CSA output. Its value is also chosen depending on the incoming pulse polarity. FBK sets the voltage level of the preamplifier output. FBK is very sensitive to chip temperature. [1]
CSA: Charge Sensitive Amplifier. A sensitive amplifier that can detect the presence of electrons in very small quantities, of the order of a few hundreds or thousands. Used in Medipix to amplify the tiny pulses from ionisation caused by x-ray photons.

GND: GND is a voltage reference. GND sets the “virtual ground” level of the pixel electrode; its value is chosen to match the polarity of incoming pulses, according to the presence of a positive or negative high voltage bias. [1]


Ikrum: This value sets the rise time of the pulse. A higher IKrum means a shorter rise time and a higher pulse, increasing the electronic noise. Electrical noise is normally a significant problem because it competes with and masks the tiny charge pulses form a radiation detector. [4]

Preamp: The purposes of a preamplifier (or preamp) are 1) to amplify, if necessary, the relatively small signals produced by the radiation detector, and 2) to shape the signal pulse for optimal signal processing by the subsequent components.

LVDS: The LVDS (Low Voltage Differential Signaling) is a low swing differential technology which allows single channel data transmission at very high speeds. LVDS delivers high data rates while consuming significantly less power than other technologies. In addition, it brings many other benefits such as low-voltage, power supply compatibility, low noise generation, high noise rejection, robust transmission signals and the ability to be integrated at chip system level. [3]

While it is unlikely this could be something called an LVDS refresh rate used to save power.

Threshold (THL): The adjustment of the minimum energy of particles detected by the chip. The higher the value, the lower the threshold, as the THL acts as the denominator of a fraction. Too high a threshold can cause the chip to "white-out".

THL (Threshold) Coarse:

THS: By adjusting the value of THS you can ensure accurate results are recorded even if the difference between the actual distance and optimal distance is too great.

Vcas: A global 8-bit voltage DAC which controls the biasing of cascode.
Cascode: is an amplifier consisting of a common emitter input stage that drives a common base output stage. (This means there is high gain and low noise.)

IHist: needs to be edited "Ihist" controlls the switch which opens a diode transistor. This switch turns on a negative current which generates a hysteresis effect. The discrimantor hysteresis can be easily turned of by reducing the Ihist current to 0.


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