Will an inductive load damage my function generator? Will the circuit I'm designing damage my function generator shown below.

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I'm using this function generator which has an output impedance of 50 ohms: https://www.gsi-protek.com/9205a9205c

  • \$\begingroup\$ What do you think the voltage and current will be with say 1ns rise time \$\endgroup\$ Apr 27, 2017 at 3:00
  • \$\begingroup\$ I think the voltage and current will be essentially 0???? \$\endgroup\$
    – Guy Lee
    Apr 27, 2017 at 3:10
  • \$\begingroup\$ totally wrong . what is the impedance formula? \$\endgroup\$ Apr 27, 2017 at 4:29
  • \$\begingroup\$ Z_Load = jOmegaL \$\endgroup\$
    – Guy Lee
    Apr 27, 2017 at 4:35
  • \$\begingroup\$ What is your function generator? At low frequencies the load will look close to a short circuit and about 7.5 ohms at 10kHz. I would expect most function generators to cope with this OK but check the data sheet. \$\endgroup\$ Apr 27, 2017 at 5:47

2 Answers 2


It should be just fine.

Your function generator will look like a low source impedance 400mV p-p source (like an op-amp output but beefier) with a 50 ohm resistor in series, so the complete circuit is not purely inductive (not that it's a problem).

The inductor has an impedance of \$2 \pi f L\$ for a sine wave or about 7.5 ohms.

Any decent commercial function generator should not be damaged by even shorting the output or connecting it to arbitrary impedances, and these levels are pretty benign. 4mA peak into even a short circuit is nothing to be concerned about. Don't try a 100uF capacitor charged to 300VDC though. Your function generator can supply 100mA peak into a 50 ohm load.


120uH is similar to that of a tweeter with ~8 Ohms @10kHz.

The manual specs indicate 20Vp no load and 5Vp into 50 Ohms max or 0.5W. So 100mVp is SAFE.

Since 8 Ohms reflects more signal from a 50 Ohms source , it appears to attenuate 8/58 or 14% rather than 50% of the no load signal for a matched impedance. Thus 86% of the no load signal is dissipated which has a ratio of 86/14=6.1.

With 10Vp from the gen, no load, it will be it's max rated value at 5Vp into 50Ohm load for 0.5W dissipated in both gen and load or 1W total but only 14% in VAR to your reactive load, your max output power should be 140mWp or 1.02Vp (max) into 8 Ohms at 10kHz.

But then as f drops your max voltage to load must drop a bit due to the impedance ratio.

The DCR of the coil may be in the mOhm range and therefore DC is critical to be included as well in your calculations.

If this is relevant to your situation, update your question and include waveshape.


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