Not sure I'm in the correct forum, but I see nothing else that fits.
The circuit is for a Q meter, the commercial units have a very low drive impedance of 0.02Ω to 0.001Ω.
The voltage is 20mv to 30mv. The source voltage will be a standard 50Ω signal generator driving a 50 to 1 wideband transformer
The problem, designing a flat transformer for 50kHz to 30MHz and keeping output constant with the change of load.
I have wound a few transformers 50 to 1 (2500 to 1 impedance ratio, 50Ω in 0.02Ω out) with maybe a 4db drop at 30MHz, and considerably less drop with reasonable change of load.
So, I think the best way to approach these two problems is to control the input voltage to keep the output voltage constant.
I started by looking at the H11F1, but it has about 100Ω to 200Ω minimum resistance, I can't work out any way to get a minimum and maximum change to make those work.
Is there another chip that has a lower on resistance the will pass RF?
I posted a block diagram of my initial thought.
Any other approach you would take
Thanks, Mikek
The circuit is for a Q meter, the commercial units have a very low drive impedance of 0.02Ω to 0.001Ω.
The voltage is 20mv to 30mv. The source voltage will be a standard 50Ω signal generator driving a 50 to 1 wideband transformer
The problem, designing a flat transformer for 50kHz to 30MHz and keeping output constant with the change of load.
I have wound a few transformers 50 to 1 (2500 to 1 impedance ratio, 50Ω in 0.02Ω out) with maybe a 4db drop at 30MHz, and considerably less drop with reasonable change of load.
So, I think the best way to approach these two problems is to control the input voltage to keep the output voltage constant.
I started by looking at the H11F1, but it has about 100Ω to 200Ω minimum resistance, I can't work out any way to get a minimum and maximum change to make those work.
Is there another chip that has a lower on resistance the will pass RF?
I posted a block diagram of my initial thought.
Any other approach you would take
Thanks, Mikek