3. Read Out Noise.

The readout noise was characterised for all outputs in both hi-gain and lo-gain mode. These modes were selected by switching the voltage on OG2 so as to vary the output node capacitance.

The output sensitivities of the CCDs are shown below in mV/electron.
 
CCD
 Left Output
Hi-gain Sensitivity		 Right Output
Hi-gain Sensitivity		 Left Output
Lo-gain Sensitivity		 Right Output
Lo-gain Sensitivity
1
2.95
3.3
1.1
1.1
2
2.8
4.15
1.2
1.4
 

The RMS noise is tabulated below for a variety of CDS integration times. In all cases the CDS RC constant was 4.3ms. Both CCDs gave significantly higher gain and lower noise with their right hand outputs.
 
 
 
 
CCD 1 in Hi-Gain
8+8ms CDS time
6+6ms CDS time
4+4ms CDS time
Left Output
4.1e 
3.8e 
5.2e 
Right Output
3.3e
3.5e
3.5e

 
 
 
CCD 2 in Hi-Gain
8+8ms CDS time
6+6ms CDS time
4+4ms CDS time
Left Output
4.4e 
4.9e 
6.2e 
Right Output
3.2e
3.5e
4.1e
 
 
 
CCD 1 in Lo-Gain
8+8ms CDS time
6+6ms CDS time
4+4ms CDS time
Left Output
9.8e 
  
10.5e 
Right Output
    
8.6e
 
 
 
CCD 2 in Lo-Gain
8+8ms CDS time
6+6ms CDS time
4+4ms CDS time
Left Output
10.0 
  
13.2e 
Right Output
    
10e
 
 

Noise and gain are critically dependent on the operational voltages. In particular the output FET drain and image area clock- low should be set to within 100mV of the voltages recommended in Appendix A.