What is so special about an injection transformer and why should I buy one, it is pretty expensive?
A good injection transformer has high flux capacity, very good coupling, adequate isolation voltage and sufficient permeability to allow the low frequency injection. Most injection transformers, as well as the audio transformers engineers often try to use don’t have the necessary bandwidth and so at low frequencies and high frequencies the signal gets very noisy and finally inaccurate. These transformers are often ferrite, which does not offer very high permeability and the isolation is relatively low voltage (50V or 100V) The Picotest transformers are rated for category II certified for 600V isolation, allowing them to be used for PFC’s and most offline measurements. The Picotest transformers also use a specially annealed amorphous nanocrystaline core, offering very high permeability and allowing the low frequency and high frequency performance needed for high fidelity measurements.
Picotest offers two transformers, the J2100A and the J2101A. The difference between the two transformers is the bandwidth. The J2100A offers a low end bandwidth of 1Hz satisfying low frequency measurements such as PFCs, while the J2101A is designed for a higher frequency range starting at 10Hz. The J2101A is most beneficial for linear regulators, LDOs and switching regulators.