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FAQ #13: Which measurements (Output impedance Vout/Iout, audio susceptibility Vout/Vin, input admitt

Which measurements (Output impedance Vout/Iout, audio susceptibility Vout/Vin, input admittance Iint/Vin and reverse transfer Iin/Iout, loop gain are we are able to perform utilizing our HP gain-phase analyzer and your injectors?

The simple answer is all of them!  This of course depends on which injectors you purchase.  The best way to measure output impedance (and small signal step load response) as well are reverse transfer (and also crosstalk) is with a current injector.  The current injector can also be used to measure input filter Q (or stability), especially in cases where it is connected to a negative resistance load, such as a switching power supply.   In some cases the current injector can also be used to measure PSRR.  The phase margin of a voltage regulator can be measured, even without access to the control loop.  This is a simple measurement using the current injector with the Bode-100, since the Bode-100 software has the algorithm to make this a cursor measurement.  So the current injector is one of the most versatile.

Measurement of the control loop requires either an injection transformer, such as our J2100A or J2101A or for wider bandwidth or lower noise measurements the J2110A is an excellent solution.  Since accurate Bode measurements require very small signals, it is often necessary to use an attenuator to reduce the signal levels.  The J2140A offers 10dB-70dB attenuation in 10dB steps.

The J2120A Line injector is specifically designed for audio susceptibility testing (PSRR) and can support load currents up to 5A and voltages up to 50V.

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