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   Injector Series

Home > Products> J2120A
     J2120A Line Injector

 
icon 10Hz-10MHz usable bandwidth
icon Low loss design
icon 5 Amps maximum current
icon 50VDC max input
icon Easily measure input filters and PSRR
icon Detailed Specifications
 
  Product Information

While the injection transformer is a very wideband adapter, it is not useful for measuring ripple rejection (PSRR) of a power supply or even an opamp. 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 (J2120A) is another essential test adapter.

The line injector allows the input DC supply voltage to be modulated by the network analyzer source signal, as in the case of a PSRR measurement. The line injector must be capable of a frequency range well below the AC line frequency and at least above the control loop bandwidth of the circuit being tested.

The line injector is only capable of sourcing current, so that the output amplitude can be significantly impacted by the operating current and the total storage capacitance at the load. The network analyzer has a very high selectivity so distortion at the output of the line injector generally does not influence the measurement. Again, this is a small signal injector, so the oscillator signals should be kept as small as possible above the noise floor. As a guide, try to keep the input signal amplitude below 50mVpp (-20dBm). In some cases we want to attenuate the source signal even further, and so we have included the attenuators in the injector kits. Some analyzers, such as the Omicron-Lab-Lab Bode-100 allow shaping the injection amplitude as a function of frequency, which helps optimize the signal level.

Measuring Output Impedance

The line injector can also be used in conjunction with a current probe to measure the input impedance of a power supply. The input impedance of a switching power supply or regulator is negative, which is a stability concern when combined with an EMI filter, making the measurement an important part of the design, analysis and verification process. The current probe must be set for 1A/V or the results need to be scaled accordingly for different settings.

 
  Detailed Specifications:
Specifications
Characteristic Typical
Maximum DC Input Voltage 50VDC
Maximum Continuous Current 5A
Maximum Voltage Drop 3.25VDC
3dB Frequency Response 15Hz ~ 5MHz
Useable Frequency Response 10Hz ~ 10MHz
Recommended Injection Signal -20dBm ~ 10dBm
Temperature Range 0 ~ 50°C
Maximum Altitude 6000 Ft

 

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