THE FORWARD CHARACTERISTIC OF THE PIN DIODE 691 



0Vo 



n.y = ppe 



Equations (13) can be written 



/. -f- 6/, 



dn In — bl-o 



dx 2Dn 



where b = Dn/Dp . Combining (19) and (21) gives the equations 



Ho = niHn/Insf"" 

 Tin, = 7li(Ip/IpsY'' 



where nf = rippp is a constant, and also 



/3Fo = Vz (n -^ ^ 



Pp ^ns 



Up Ips 



(18) 



Under conditions of large injection we can say 



n» P, p» P 



rioo » np Pww » Pn 



so that (11) becomes 



In = Insirioo/np'^) 



^p — J^ psKPww/pN ) 



and (17) becomes 



n{x) = p{x) ^ X ^ w (20) 



Equation (16) becomes 



7ioo = Uo^np /np)e 



(19) 



(21) 



(22) 



(23) 



(24) 



I'^rom the first equation (22) we have 



SY, = k+J^ f A^ (25) 



2Dn .'o nix) 



