• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 49 subscribers
  • Views 2396 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TINA/Spice/OPA548: opa548 - Howland Pump - 2.5 Amps - 50 KHz

Mubeen Haadi
Prodigy 100 points
Part Number: OPA548
Other Parts Discussed in Thread: TINA-TI

Tool/software: TINA-TI or Spice Models

Hi,

I am trying to design a howland current pump to feed an induction coil (inductance not known, resistance .25 Ohms). The output current have to be 2.5 Amps (peak), the voltage amplitude and shape is irrelevant as long as the shape of the current is sinusoidal. The input voltage signal is 2.5 V (peak to peak) Sinusoidal. The following design full fills the requirement regarding the current but only at low frequency i.e upto 150 Hz.

How can I modify the design to get the same output (2.5 Amps peak) for the same input (2.5 V peak to peak) but at higher frequency let's say 50KHz

Design_02.TSC

  • 0
    TI__Mastermind 23050 points

    Hi Mubeen,

    I don't believe it is possible for this circuit to drive 2.5A into a 10mH inductor at 50kHz. The problem is at 50kHz a 10mH inductor has an impedance of 3.14kOhms. The op amp is not capable of providing the voltage levels necessary to drive that much current into that large of a load (by Ohms law this would require 7.85kV!). If you need to operate near 50kHz you will either need to use a much smaller coil or drastically decrease your current requirements. 

    Regards,

    Zak Kaye

    Precision Amplifiers Applications

  • 0 in reply to Zak Kaye
    Prodigy 100 points

    Hello,

    I understand the howland pump a little better now. I have developed the following circuit. it is working fine in simulation, but works terribly when I built it on bread board. can you suggest a solution?

    the screen shot with clear sine signal is when I connect a 1.1 ohm resistor as load, the other screen shot is when I connect toroid transformer (287.5uH + .5 ohm) as load. I need a clear sine signal as in simulation. Any ideas on how to fix this?