Consequently, we have V bf = V bi V a , f = Q af C a = Q ai - ?? ??? ??? Q a C a = Q ai - ?? ??? ??? Q b C a = C a ??? V ai - I ??? ??? ??t C a = C a ??? Vpcx - I ??? ??? ?? ??? ??? t C a and hence V a , f = Vpcx - I ??? ??? ?? ??? ??? t C a ( 1 ) In practice, there is a linear relation between the final voltage Va on the charge-integration node 28 and the current absorbed by the current source 10