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What's included:

J2121A High Power Line Injector
1 ohm Calibration Fixture
J2171A 200mA Low Noise Power Supply
User manual
1 Year Warranty



  • 400V/20A max – Supports High Power 270V Military and Satellite Buss Applications
  • 100Hz - 1MHz bandwidth
  • Regulated Input-Output Voltage Drop, 500mV
  • Isolated Current Sense Monitor Output
  • Fan cooled, Includes low-noise power supply



  • Power Supply Rejection Ratio (PSRR) Measurements
  • Inductor DC Bias Measurements (up to 20A)
  • DC-DC Converter Input Impedance Testing
  • Line Injector Comparison - J2121A vs. J2120A
    • J2121A supports much higher voltage and current applications
    • J2120A has ultra-low noise output, 50V/5A max 10MHz bandwidth, passive, variable voltage drop (1.5V-3.5V) based on the load impedance
    • J2120A favors PSMR and low current, low voltage, PSRR measurement applications
    • The J2121A has a much higher voltage range, much higher current rating and integrated Hall current monitor
    • The J2121A favors high voltage, high current PSRR testing and DC/DC and Inductor impedance measurement


While the injection transformer used for Bode plots is a very wideband transformer, it is not useful for measuring ripple rejection (PSRR) of a power supply or even an opamp. Doing so could permanently damage the transformer. This is because the attributes that make the injection transformer perform so well also result in a transformer that is intolerant of DC current. Even very small DC currents (5mA or less) can greatly reduce the signal capacity or even totally saturate the transformer. For this reason, the Picotest line injector (J2121A) is another essential test adapter for power supply testing.

The J2121A is especially suited to high power applications such as those associated with military and satellite busses. It can be used with input bus voltages up to 400V and supply up to 20A at 1MHz. The line injector allows the input DC supply voltage to be modulated by the network analyzer source signal (oscillator). The J2121A line injector output is DC regulated and provides a fixed voltage drop of 750mV from the input bus voltage fed into the injector in addition to the AC modulation signal.


The J2121A can be connected to the power supply input under test and, depending on the test probe connection points, can be used to measure either PSRR or the power supply’s input impedance The line injector can also be used to measure the impedance/inductance of an inductor under bias.

While a current probe can be used as part of a test setup, the J2121A includes a current sense monitor output that can be connected to the VNA.


The J2121A comes with the J2171A power supply and connecting cable, used to power it, and a 1-ohm calibration fixture.

Picotest J2121A High Power Line Injector

  • Characteristic Typical Units
    Maximum DC Input Voltage 400 VDC
    Maximum Continuous Current 20 A
    Typical Input-Output Voltage Drop 0.75 VDC
    Transfer Gain unity gain, whatever the modulation amplitude is set to (up to ~500mVpk) is what the modulation amplitude will be at the J2121A output -
    Modulation Input Impedance 50 ohms
    Output Signal Bandwidth 100-1M Hz
    Current Monitor Bandwidth (THRU CAL) DC-1M Hz
    Current Monitor Scale (AC) 100 mV/A
    Current Monitor Termination Impedance > 10 KOhms
    Max Current Monitor DC Offset 100 mV
    Recommended Injection Signal 6 dBm
    Temperature Range 0-50 C
    Maximum Altitude 6000 Ft



    • Bus Voltage: Plus and minus, standard banana jacks female
    • Signal Modulation: BNC
    • Power: J2171A proprietary connector, cable and power supply included


    • Voltage Output: Plus and minus, standard banana jacks female
    • Isolated Current Sense Monitor: BNC


    Caution: To avoid equipment damage and/or severe injuries or death ensure that the absolute maximum ratings are observed and not exceeded at all times.

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