what i need is 0 to 2mA of current out of this current source.
I breadboarded this and it works fine when one of the 2 voltage are fed one at the time; both (0 to 12V and 0 to 5V) give me the desired 2mA.
(the OTA used is a LM13700 and the Amp bias input is 2 diodes from the negative rail)
Strange things happen when i sum them.
if i slowly increase and sum the 2 currents, the measured sum at the output first reaches 2mA, but just after that it starts to decrease untill it reaches 1.6mA when the 2 currents are at the maximum.
i was expecting them to be linearly summed and being limited by R14.
i don’t understand why this occurs
I breadboarded this and it works fine when one of the 2 voltage are fed one at the time; both (0 to 12V and 0 to 5V) give me the desired 2mA.
(the OTA used is a LM13700 and the Amp bias input is 2 diodes from the negative rail)
Strange things happen when i sum them.
if i slowly increase and sum the 2 currents, the measured sum at the output first reaches 2mA, but just after that it starts to decrease untill it reaches 1.6mA when the 2 currents are at the maximum.
i was expecting them to be linearly summed and being limited by R14.
i don’t understand why this occurs
Attachments
-
48.1 KB Views: 21