Probably the only way to safely connect test equipment to SMPS for analysis, the Picotest transformers work effectively well over the frequency range needed for demanding test and will work with virtually any bode plot analyser or suitable oscilloscope and tracking generator combo.
I used them recently and both gave as near an ideal result as can be expected with both being easy to work with, not requiring exemplary knowledge to set up and use. All in all, these devices are an excellent investment and very efficient with results accurate and repeatable.
The J2101A Injection Transformer is presently the prevalent method for connecting the network analyzer to the circuit being tested, and is primarily used for control loop stability measurements. The goal of the transformer is to inject a signal into the control loop being measured, without impacting the performance of the loop. In order to accomplish this to a reasonable degree, The transformer is isolated and therefore is capable of floating on a high voltage, such as a Power Factor Corrector (PFC), which is often close to 400VDC. Measuring voltages that exceed the voltage rating of the FRA inputs require attenuation probes.
The usable bandwidth of an injection transformer is generally significantly greater than the 3dB frequency limits. This is because the transformer itself is outside of the measurement, leading many to incorrectly believe that the transformer is a non-critical element.
The bandwidth of the transformer is strongly related to the terminating impedance. The most network analyzers provide a 50 Ohm oscillator source impedance. Assuming this impedance the optimal termination resistor is 5 Ohms. This significantly attenuates the injection signal, which is generally beneficial, as a common error in Bode measurements is using a signal which is too large, and therefore not a small signal measurement. An added benefit of this low value is that it can generally be left in circuit at all times, simplifying the connection to the network analyzer without appreciably impacting the output voltage of the circuit being tested.
| Performance at -10dBm input level | |
| Characteristic | Rating |
| DCR | |
| Ratio | 1:1 |
| Termination Impedance | 5 Ohms |
| Usable Bandwidth | 10Hz - 45MHz (Terminated into 5 Ohms) 60Hz - 45MHz (Terminated into 50 Ohms) |
| Isolation Voltage | 600V |
| Isolation Capacitance | 150pF@1KHz |
| DC Current | 10mA |
| Temperature Range | 0 ~ 50°C |
| Maximum Altitude | 6000 Ft |
Note: The upper end of the bandwidth is heavily dependent on the interconnect between the Injector and the DUT.
- condition: new - custom_product: false - mpn: J2101A - google_product_category: Electronics - key_feature_2: Wideband Frequency Range - key_feature_3: Low Distortion Injection - key_feature_4: High Isolation Voltage - key_feature_5: 1:1 Transformer Ratio - key_feature_6: Compatible Termination Impedance - myordercount: {"ordercount":1,"recentcount":1} - rating: {"scale_min":"1.0","scale_max":"5.0","value":"5.0"} - rating_count: 1 - warranty: 12 months - brand: Picotest - target_keyword: Picotest J2101A - manufacturer: PicoTest Corp - breadcrumbs: ["gid://shopify/Collection/267180835005"] - review_snippet_widget: - brands: gid://shopify/Metaobject/56256102623 - customhs_code: 903090 - detailed_description: {"type":"root","children":[{"type":"heading","level":1,"children":[{"type":"text","value":"Product Information"}]},{"type":"paragraph","children":[{"type":"text","value":"The "},{"type":"text","value":"J2101A Injection Transformer","bold":true},{"type":"text","value":" is presently the prevalent method for connecting the network analyzer to the circuit being tested, and is primarily used for control loop stability measurements. The goal of the transformer is to inject a signal into the control loop being measured, without impacting the performance of the loop. In order to accomplish this to a reasonable degree, The transformer is isolated and therefore is capable of floating on a high voltage, such as a Power Factor Corrector (PFC), which is often close to 400VDC. Measuring voltages that exceed the voltage rating of the FRA inputs require attenuation probes."}]},{"type":"paragraph","children":[{"type":"text","value":"The usable bandwidth of an injection transformer is generally significantly greater than the 3dB frequency limits. This is because the transformer itself is outside of the measurement, leading many to incorrectly believe that the transformer is a non-critical element."}]},{"type":"paragraph","children":[{"type":"text","value":"The bandwidth of the transformer is strongly related to the terminating impedance. The most network analyzers provide a 50 Ohm oscillator source impedance. Assuming this impedance the optimal termination resistor is 5 Ohms. This significantly attenuates the injection signal, which is generally beneficial, as a common error in Bode measurements is using a signal which is too large, and therefore not a small signal measurement. An added benefit of this low value is that it can generally be left in circuit at all times, simplifying the connection to the network analyzer without appreciably impacting the output voltage of the circuit being tested."}]},{"type":"paragraph","children":[{"type":"text","value":""}]},{"type":"heading","level":2,"children":[{"type":"text","value":"Detailed Specifications"}]},{"type":"paragraph","children":[{"type":"text","value":"Performance at -10dBm input level\nCharacteristic\nRating\nDCR\nRatio\n1:1\nTermination Impedance\n5 Ohms\nUsable Bandwidth\n10Hz - 45MHz (Terminated into 5 Ohms)\n 60Hz - 45MHz (Terminated into 50 Ohms)\nIsolation Voltage\n600V\nIsolation Capacitance\n150pF@1KHz\nDC Current\n10mA\nTemperature Range\n0 ~ 50°C\nMaximum Altitude\n6000 Ft"}]},{"type":"paragraph","children":[{"type":"text","value":"Note: The upper end of the bandwidth is heavily dependent on the interconnect between the Injector and the DUT."}]}]} - summary:The Picotest J2101A Wideband Injection Transformer (SKU: J2101A) enables safe and precise injection of test signals into the control loops of DC-DC converters and power supply systems, making it invaluable for stability, gain, and phase margin measurements. Spanning a frequency range from 10Hz to 45MHz and supporting off-line power supplies, the J2101A suits both low- and high-frequency power integrity testing scenarios.
Primarily used for Bode plot and loop response analysis, the J2101A provides a low-distortion, galvanically isolated signal path between a network analyzer and the device under test. Its 1:1 ratio, 600V isolation voltage, and robust 5 Ohm termination assure compatibility with most analyzers and power electronics, including power factor correctors (PFCs), switching regulators, and LDOs.
The J2101A forms part of Picotest’s comprehensive injector family. Consider the J2100A for ultra-low frequency needs, or the J2110A Solid State Injector for DC to 45MHz bandwidth with ultra-low noise and higher precision.
Its unmatched balance of wide bandwidth, robust isolation, and low distortion ensures reliable performance and minimal impact on the circuit. Engineers who require accurate, repeatable measurement of control loop stability in modern high-speed designs consistently value the J2101A.
- key_feature_1: High-performance transformer for loop injection, stability and frequency response measurements. - key_feature_2_tooltip: {"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"The J2101A offers a full 10Hz–45MHz bandwidth, making it suitable for both low-frequency and high-speed regulator testing.\">Wide operating frequency enables analysis across varied applications—ideal for modern electronic designs."}]}]} - key_feature_3_tooltip: {"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Low distortion ensures minimal impact on control loop stability, so measurements accurately reflect circuit performance.\">Measures without adding artefacts, delivering precise, unbiased loop stability data every time."}]}]} - key_feature_4_tooltip: {"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"600V galvanic isolation allows testing in high voltage environments, supporting offline PSU and PFC circuits safely.\">Safely inject signals without risking circuit or operator safety in demanding scenarios."}]}]} - key_feature_5_tooltip: {"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Provides predictable signal injection without gain or loss, maintaining measurement consistency in all setups.\">Simplifies test configuration and guarantees reliability in results.\n\n"}]}]} - key_feature_6_tooltip: {"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"5 Ohm nominal termination matches most network analyzers and minimises the risk of signal distortion or attenuation.\">Plug-and-play usability for popular measurement setups."}]}]} - key_feature_7: Robust Construction - key_feature_7_tooltip: {"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Compact design with durable connectors ensures long service life and reliable connections even under frequent use. Engineered for repeated, professional-grade operation in busy labs."}]}]} - key_feature_8_tooltip: {"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Part of an extensive family of Picotest injectors, allowing optimal matching to a variety of test and measurement needs.\">Seamlessly integrates with other Picotest products for a complete measurement solution."}]}]} - key_feature_8: Series Integration - why_people_choose_3_title: Safety and Ease of Use - why_people_choose_2_title: Versatile Frequency Coverage - why_people_choose_1_title: Precision Stability Analysis - why_people_choose_1: Delivers consistent, low-distortion signal injection critical for accurate Bode plot and loop stability measurements. - why_people_choose_3: 600V isolation and rugged construction provide peace of mind during test in demanding or high-voltage environments. - why_people_choose_2: One transformer covers both low and high frequency applications; complements tools like the Dediprog J2100A. - 1566797: What is the frequency range of the Picotest J2101A Injection Transformer?***SIMP***The J2101A operates from 10Hz to 45MHz, supporting a broad range for DC-DC converter and regulator measurements. - 1566799: Can the J2101A be used for offline power supply stability testing?***SIMP***Yes, with its 600V isolation, it is suitable for high-voltage and offline PSU applications. - 1566800: What terminations are recommended for the J2101A?***SIMP***The transformer is optimised for 50 Ohm termination but is compatible with most standard 50 Ohm analyzers.
- 1566804: How does the J2101A compare to Picotest’s J2100A?***SIMP***The J2100A covers lower frequencies down to 1Hz; the J2101A spans higher frequencies up to 45MHz for faster regulators. - 1566806: Can the J2101A be left permanently in-circuit?***SIMP***Its low termination value allows it to remain in-circuit during normal operation without affecting the output voltage. - 1566807: Is the J2101A compatible with all network analyzers?***SIMP***Yes, it integrates seamlessly with most mainstream network and impedance analyzers. - 1566808: What’s the benefit of 1:1 transformer ratio?***SIMP***Ensures that injected signals are neither amplified nor attenuated, supporting precision measurements. - 1566810: Are there solid-state options in the Picotest range?***SIMP***The J2110A Solid State Injector provides DC–45MHz bandwidth and is suitable for ultra-low noise applications. - 1566811: What is the maximum DC current rating?***SIMP***The J2101A supports up to 10mA DC current before inductance drops 10%. - 1566812: What’s the recommended alternative for ultra-low frequency injection?***SIMP***The Picotest J2100A is suited for frequencies as low as 1Hz.