Good day team,

I need to design an AC amplifier for an inductive load (coil). Here are the specifications:

1. Frequency: 35-55KHz
2. Current 1,5A
3. Inductance of coil: 100mH

I have done some research, I need to factor in the impedance of the inductor at this frequency. Xl = 2*pi*F*L. Even knowing this value, how best can I design a circuit that pumps 1,5A through this coil at this frequency?

Hello, I am working on an amplifier for a Helmholtz coil and I was wondering if you could share your design? I am trying to use a class D amplifier and came across this thread thinking it would be a good start

MOD NOTE: Split from https://forum.allaboutcircuits.com/...gn-for-an-inductive-load.195603/#post-2003044

 

As stated in the previous thread:
Impedance of coil at 55kHz = 34kΩ
Voltage required for 1.5A in 34kΩ = 51.8kV.
. . but 100mH seems a lot for an air-cored coil

 

I am working on an amplifier for a Helmholtz coil and I was wondering if you could share your design?

Give us all the data you have. I assume you are not doing the exact same thing as the other post.
What supply voltages are available?
What current?
Inductance?
Resistance of the coil?

 

Give us all the data you have. I assume you are not doing the exact same thing as the other post.
What supply voltages are available?
What current?
Inductance?
Resistance of the coil?

Coil inductance: 11.93 mH
Coil DC resistance: 35.2 mOhms
Frequency: Targeting DC to 100khz
Current output: +- 25 amps AC
Voltage drive; 60 Vp2p

Essentially the scope of my project is to create a high current amplifier to drive a Helmholtz coil to produce a magnetic field. Meeting these requirements seems impossible with my current knowledge so I want to start with smaller currents/frequencies to gain more experience and work up from there.

 

Coil inductance: 11.93 mH
Coil DC resistance: 35.2 mOhms
Frequency: Targeting DC to 100khz
Current output: +- 25 amps AC
Voltage drive; 60 Vp2p

Essentially the scope of my project is to create a high current amplifier to drive a Helmholtz coil to produce a magnetic field. Meeting these requirements seems impossible with my current knowledge so I want to start with smaller currents/frequencies to gain more experience and work up from there.

I will also be adding capacitive compensation to "cancel" out the inductance later on but I want to see if i can at least achieve a few amps without capacitive comp

 

Just do the maths:
Inductive reactance = 7496 Ω at 100kHz
Voltage required for 25A = 187400V rms = 530000V peak-to-peak
You're 529940 Volts too low.

 

Coil inductance: 11.93 mH
Coil DC resistance: 35.2 mOhms

It has been a while since I made a Helmholtz coil. What size, how many turns?
This looks like a hell of a big radio transmitter in the LF band.

 

For a somewhat different approach, start by calculating the power required to force that much current thru the coil, at the desired frequency. Then you will know the amplifier power needed. After that you need to design a matching network. Good news there, that is a topic with lots of information available. Actually building it will probably be a challenge, though, depending on your resources.