Signal transformers — wideband, balun, current transformer

One transformer circuit: the primary takes the signal source or a through-core current, the secondary drives the load. The brackets after each band give the scenario (signal/CT); MnZn high-permeability in the low bands, NiZn above 1 MHz.

TWideband signal transformer / balunMnZn high-permeability up to 1.5 MHz, TM63 for 1–5 MHz; above that NiZn along the μi ladder
CTCurrent transformersThe primary is often a single turn through the core; high μi and low remanence keep the magnetizing current small and the measurement accurate

CIRCUIT · SIGNAL

Band → material

Band	First choice	Alternative	Note
≤1.5 MHz (signal)	T05 T10	E02 T12	MnZn high-perm, chosen by μi
1–5 MHz (signal)	TM63	TM61 TM65★	Low-power wideband transformers with large signal swing / high bias
≦1.5 MHz（CT）	T10 T07	T05 T06 E02 T2
1–5 MHz（CT）	—	TM63	MHz CTs (CT)
≤0.5 MHz (pulse/gate)	TM71	T05	High μi and high Bs for ungapped pulse / gate-drive cores
1–5 MHz (pulse/gate)	—	TM63	MHz gate drive
NiZn 1–2 MHz (signal)	DL3 DL4	—	Low-band baluns / wideband signal (catalogue frequency range)
NiZn 1–3.5 MHz (signal)	Q1C1	—	Upper limit = lower of loss factor ≤2× its minimum and μ′ within 20 % of nominal
NiZn 1–6.7 MHz (signal)	M63	—
NiZn 1–7.7 MHz (signal)	M61	—
NiZn 1–15 MHz (signal)	—	M61H
NiZn 1–25 MHz (signal)	M9A	—
NiZn 1–30 MHz (signal)	V2F1	—
NiZn 1–50 MHz (signal)	—	M5E1	Upper limit = lower of loss factor ≤2× its minimum and μ′ within 20 % of nominal
NiZn 1–55 MHz (signal)	—	V4F1
NiZn (CT)	—	—	No NiZn counterpart
NiZn (pulse/gate)	—	—	No NiZn counterpart

Suggested shapes

3D · illustrativeToroid TChoose a series ▾

Strengths

Closed magnetic path without joints or air gap: highest magnetic efficiency
Good self-shielding, low leakage flux
Lowest core cost, no bobbin needed

Trade-offs

Winding must be threaded through the hole; high winding cost
Less convenient to mount on the PCB
No air gap; for storage inductors use a combination shape whose gap can be ground

T Core MnZn T CORE NiZn