1. Bifilar Wound Toroids Session 2
Ferrite Transformers for Matching Amplifiers
Ferrite Cores for Transmission Lines/Baluns, EMI
Powdered Iron High Q inductors: Increased Inductance
FT :1 Transformer
Ferrite

2. Operating Principles Right Hand Rule
For a Solenoid
Reversing Current Direction Reverses the Flux
B [tesla] B
I [Amps]
L1 [H]
I [Amps]

3. Operating Principles Right Hand Rule
For a Solenoid
A simple Experiment with a compass
Demonstrated in Lab

4. Ideal Transformers N1=N2 Identical Windings Lenz and FaradayB1
Lossless
1 mA
B1+B2 =0
1 mA B2

5. Series Connection of Inductors Bifilar Winding: Additive L1=L2 Leq= L1+L2+2M Leq = 4L1 if M = L1
Wind one Inductor: 10 Turns Bifilar
Lead Length = 1.5 inches
Don’t solder windings yet
Measure Single Turn Inductor LC mtr
Solder Connections
Measure Bifilar Inductor LC mtr
Measure input impedance with AIM
Compare Single turn and Bifilar Inductance
Lbifilar
#26 Gauge
Yellow Core

6. Winding Bifilar Inductors Additive
Layout wires per top left drawing. Check continuity
Connect per top right: Solder “a dot” to b

7. Series Connection of Inductors Bifilar Winding: Subtractive L1=L2 Leq= L1+L2 - 2M Leq = 0 if M = L1

8. 4:1 Ferrite Transformer Bifilar Wound
Zin = 50 Ohms Zload = 200 Ohms b a
2 mA b a
Subtractive Currents
No flux in Toroid
1mA
1mA
1 mA
Make one transformer: 10 Turns FT50-43 material
Use #26 Gauge wire and supplied BNC connector
Measure input impedance with AIM Impedance meter

9. 4:1 Ferrite Transformer Bifilar Wound
Zin = 50 Ohms Zload = 200 Ohms a b b a
b is ground.. Bend end up to label
a dot is connected to 200 Ohm resistor
Connect b dot to a : insert into center pin of connector