FAQ #23 What Injectors do I need for PDN Measurements?

Our J2112A current injector has been the most requested product to date.  It provides a very fast low current pulse, though based on a RF BJT transistor with a 100MHz bandwidth loop, the interconnection can be a challenge.  An introductory application note is posted in this Publications section.  The J2112A works reasonably well at 1V, but many of our customers are now asking for 10A and 0.6V, which is not likely given BJT saturation characteristics and finite interconnect inductance.  We are working on a very different solution for lower voltage applications.  Some of our customers use our current injectors for non-invasive PSRR testing, evaluating the input filter stability or for PI/SI sensitivity testing (by generating a transient on the bus and looking for disturbance effects).

The J2110A is a solid state signal injector with a DC-100MHz bandwidth.  Similar to a “Bode Box” it offers the highest fidelity Bode plots.  We use this more for opamps and linear regulators, but it provides higher resolution than an injection transformer.  We do make very good, wideband injection transformers as well (J2100A/2101A).  We recommend terminating these transformers into 4.99 Ohms and not 50 Ohms.


The J2180A preamp is 0.1Hz-100MHz and is nearly noiseless at 2.4nV/rt-Hz, so it improves the SNR of most analyzer measurements by 20dB with a 20dB increase in sensitivity.  The J2180A presents a 1MegOhm input impedance and 50 Ohm output impedance and so it is very useful for connecting sensitive circuits to 50 Ohm test equipment as well.

The J2102A is a very wideband common mode transformer, maintaining good transmission line characteristics  to nearly 500MHz.  We use this for our 2 port measurements, since the Bode 100 does not have semi-floating or floating inputs.

We also have  a J2130A DC Bias injector (capacitor bank and resistor bias).  We use this primarily for measuring low power AC coupled single port reflection measurements, for example to measure stability of opamps and voltage references, without loading these circuits with 50 Ohms.  We also use this “DC Blocker” to 50 Ohm/AC couple 2 port measurements at the intermediate bus and other higher voltage applications and for measuring ripple and transients with the highest sensitivity possible coupled as 50 Ohm AC.  We can get very high fidelity ripple measurements this way, with the measurement bandwidth approaching 1GHz and at 1mV sensitivity.

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