Hello experts,   
      
   well..am new to this field and I was given a task of designing a trans   
   impedance amplifier to detect low currents of the APD ranging from 0 to 15uA..   
   It looks simple to go ahead but the design requirements threw plenty of   
   challenges and brought me here..   
      
   Here are my design requirements:   
    Photodoide: Avalanche Photo-diode with 5pF input capacitance and 50nA dark   
   current, R=0.9 with gain multiplication factor,20....   
      
   It is biased such that cathode is connected to +28V and anode, to the input   
   terminal of the opamp...   
      
   Opamp: Must be a single supply (+5 V) and detect currents upto 12uA and   
   required bandwidth is 1MHz......   
      
   So how can I use an inverting configuration with single supply positive    
   voltage?   
   Which opamp suits for this?   
   I tried providing biasing voltage at non-inverting terminal of the opamp in   
   inverting configuration but DC level was keep varying. How can I use an   
   inverting configuration for this   
      
   The next stage of this TIA is a HPF combined with a LPF (again single supply   
   opamps and use Sallenkey topology- purpose is to limit the bandwidth strictly   
   to the 80kHz to 1MHz)..so I can either distribute the overall gain or a single   
   stage does the job...   
   Which one will be the best option to go with?   
      
   --- SoupGate-Win32 v1.05   
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