|Created||April 06, 2013|
|Last modified||April 06, 2013|
|Tags||constant-current-source currentsink opamp transistor volt-to-current-simk|
Opamp and transistor used to convert a voltage to a current. The voltage to current relationship can be tailored using the following formula:
I = Vc/R1
Set R1 to a value that will produce the desired maximum current for the desired maximum voltage input.
V2 can be set as low as Vc_max + Vcesat + Vrload_min. If using a different OpAmp, make sure it's input common mode range includes ground or if not, then use a split supply (i.e. instead of connecting the opamp V- terminal to ground, connect it to a negative supply).
BTW: Rload is a place holder for whatever device needs to be current controlled (i.e. the current sink output is at the collector of Q1).