Hi all,

I have built an F to V converter driven from 2051.

Its a two NPN trnasistors in darlington with RCs to give it a response and hold time etc. inverting mode.

I am driving its input from the PWM off a port.

It works nice over more than half the range of the voltage. At the high end of voltage (full voltage) its resolution is fairly high ( here the voltage changes in small steps) but as it progresses to lower side of the voltage, the resolution is gone (the voltage changes in leaps with the same amount of change in PWM).

Its behaviour is not linear....

Help please S.O.S.

Simon