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Differential Preamp

Differential Preamp. Stephen Kaye 2013-3-22. New Preamp Design Motivation. Move preamplifier from controller to the Vacuum Interface Board (VIB) Amplifies signal near the CCDs Larger signal less susceptible to noise during transmission

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Differential Preamp

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  1. Differential Preamp Stephen Kaye 2013-3-22

  2. New Preamp Design Motivation • Move preamplifier from controller to the Vacuum Interface Board (VIB) • Amplifies signal near the CCDs • Larger signal less susceptible to noise during transmission • Use dummy CCD output to create differential transmission • Decrease susceptibility to noise and crosstalk by creating and transmitting a differential signal

  3. Preamp Design AC Coupled Differential Input from CCD DC Black Level Clamp

  4. Preamp Design (Generic)

  5. Preamp Design - Gain • Image area full well is 275,000e- (Adjust clocks not to exceed this.) • 16 bit ADC differential input voltage range is +- 4.096V (AD7625) • Map this to 60,000 ADU, so conversion gain = 4.6e-/ADU • CCD sensitivity = 7 µV/e- • Total video gain = 1.95 V/V • All video gain is in preamp stage

  6. Preamp Design – Black Level Clamp • Switch connects AC coupling capacitors to ground • Switch activated during vertical transfers • Transients from switch are coupled to both inputs and are common mode

  7. Preamp Design - Noise

  8. Preamp Design - Noise

  9. Preamp Design – Output Impedance • Preamp is driving twinax cables • Twinax cable impedance is 100 Ω • Series resistors are 100 Ω for serial termination

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