OPA548: OPA548

Consider this TIPL training:

4. TI Precision Labs - Op Amps: Power and Temperature

Located at:

Dear Tim , Kai,

Thank you so much for your valuable inputs, i have a working circuit based on the improved Howland current pump to supply AC current to a load ( 0- 200mA) by adjusting voltage for a low load of about 20ohms it works fine. I am missing a point in the design. i thought the current output as long as it is within the OPA548 limitations could be independent of the load. i simulated with a unity gain follower as displayed Figure 9. Multi-Range Current Pump of AN SNOA474A and change the R13 value as suggested but i end up with too low output current if my load gets in the kohm range (20k) (i cannot go beyond 10 mA even if i increase the injected signal voltage).

I guess i cannot have it all in one and best is to design 2 circuits to cover my application?

Thanks

Ahmed

Improved Howland with opAmp follower.TSC

Hi Ahmed,

this has to do with the fact that the output voltage of OPA548 is limited:

200mA through a load of 1k would mean a voltage drop of 200V. This is impossible for a OPA548 which is powered by a +/-30V supply voltage.

Kai