Bifilar Wound ToroidsSession 2

– Ferrite Transformers for Matching Amplifiers – Ferrite Cores for Transmission Lines/Baluns, EMI– Powdered Iron High Q inductors: Increased Inductance

FT50-43 4:1 Transformer

Ferrite

I [Amps]

B [tesla]

L1 [H]

• Reversing Current Direction Reverses the Flux

Operating Principles Right Hand Rule

For a Solenoid

I [Amps]

B

Operating Principles Right Hand Rule

For a Solenoid• A simple Experiment with a compass• Demonstrated in Lab

Ideal Transformers N1=N2Identical WindingsLenz and Faraday

1 mA

1 mA

B2

B1

B1+B2 =0

Lossless

Series Connection of InductorsBifilar Winding: Additive

L1=L2Leq= 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

a b

Winding Bifilar InductorsAdditive

a

b

b a

a a

b b

• Layout wires per top left drawing. Check continuity• Connect per top right: Solder “a dot” to b

Series Connection of InductorsBifilar Winding: Subtractive

L1=L2Leq= L1+L2 - 2MLeq = 0 if M = L1

b a

• Make one transformer: 10 Turns FT50-43 material

• Use #26 Gauge wire and supplied BNC connector

• Measure input impedance with AIM Impedance meter

2 mA

1 mA1mASubtractive Currents

No flux in Toroid

4:1 Ferrite Transformer Bifilar WoundZin = 50 Ohms Zload = 200 Ohms

1mA

b a

b a

4:1 Ferrite Transformer Bifilar WoundZin = 50 Ohms Zload = 200 Ohms

b

a 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