antknee
New Member
Hi,
Could you check my transformer spec? I will build my first transformer with a kit from coilcraft and it is best to check i'm not barking up the wrong tree before i order!
I have an audio amp the LM3886, that I'm using to drive a capacitor. The chip doesn't like capacitive loads so the transformer is isolating the capacitor. I'll be using it at high frequencies and the voltages tend to drop off at higher frequencies so I also need to step up the voltage.
Only two things are important:
Primary impedance = 8 ohms (the chip outputs this although it can output into 4)
Secondary inductance = 750uH (I require close to this, an LC resonant circuit with a 2nF capacitor must be set up)
Frequencies to be passed are 20KHz to 200KHz. The chip will output 200KHz at the gain of x30 i'm using, I've measured it with a scope so that isn't a problem.
So the calcs I've done are Primary inductance = primary impedance/ 2ΠFr = 8/(2Π x 20,000) = 63uH
So the transformer is 63uH:750uH or 1:3.4 turns
I'm thinking a toroidal air core because I need high frequency.
What size core am I going to need? How thick should the wire be?
Any thoughts welcome.
Could you check my transformer spec? I will build my first transformer with a kit from coilcraft and it is best to check i'm not barking up the wrong tree before i order!
I have an audio amp the LM3886, that I'm using to drive a capacitor. The chip doesn't like capacitive loads so the transformer is isolating the capacitor. I'll be using it at high frequencies and the voltages tend to drop off at higher frequencies so I also need to step up the voltage.
Only two things are important:
Primary impedance = 8 ohms (the chip outputs this although it can output into 4)
Secondary inductance = 750uH (I require close to this, an LC resonant circuit with a 2nF capacitor must be set up)
Frequencies to be passed are 20KHz to 200KHz. The chip will output 200KHz at the gain of x30 i'm using, I've measured it with a scope so that isn't a problem.
So the calcs I've done are Primary inductance = primary impedance/ 2ΠFr = 8/(2Π x 20,000) = 63uH
So the transformer is 63uH:750uH or 1:3.4 turns
I'm thinking a toroidal air core because I need high frequency.
What size core am I going to need? How thick should the wire be?
Any thoughts welcome.