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# LMH6521 Inductor maximum current calculation on Figure 30.

Other Parts Discussed in Thread: LMH6521

Hallo,

The LMH6521 mentions below in page-14 with Figure 30.
“ Make sure to check the inductor datasheet to not exceed the maximum current limit. “
Could you please let me know how to calculate the inductor current?
Is it proper (bias current)+(AC inductor current) = (bias current)+(V／ωL)?
Bias current = 36mA
V= (Vp-p/2) ….. LMH6521 output Vp-p/2 voltage
ω= 3.14
L= 1uF

Best Regards,
Kazu Ogawa

• Hello Kazuhiko,

Yes. The inductor current would be = bias current + AC current = bias current + (V/wL). The bias current = 36mA, V = Vrms = Vpp/(2*sqrt(2)), w = 2*pi*f (f is operating frequency) and L = 1uH.

Best Regards,

Rohit

• ohit-san,Thank you very much for your answer.
I received another question from the customer?
Is it necessary to change the inductor value of the biasing inductor 1uF or okay to leave 1uF unchanged, according to the operating frequency when is changed?
The datasheet mentions “ With large inductors and high operating frequencies the inductor will present a very high impedance and will have minimal AC current. If the inductor is chosen to have a smaller value, or if the operating frequency is very low there could be enough AC current flowing in the inductor to become significant. “
Best Regards,Kazu Ogawa
• Rohit-san,
I mistook the unit of the inductor in the previous mail, not “ F “ but “ H “.
And,I received one another question.
Is 50-ohm correct for the input resistor in the Figure 27.of the datasheet 12-page?
I think it should be 100-ohm, as the LMH6521 input impedance is 200-ohm.
Best Regards,Kazu Ogawa
• Hello Kazu-san,

You are correct, a 100 Ohm resistor will provide the best match as shown in Figure 27.

For most applications a 1uH inductor is the best value.

Regards,
Loren
• Loren-san,Thank you very much.Best Regards,Kazu Ogawa