ampage Tube Amps / Music Electronics	For current discussions, please visit Music Electronics Forum.

ampage archive

Vintage threads from the first ten years

previous: paul perry The output impedance of a FET or tr... -- 3/4/2000 5:17 AM

Re: no subject

3/4/2000 5:01 PM
Jim	Re: no subject same guru also told me that in his e-mail too. The output z of a follower is low for both positive and negative swings. Bipolar lower than FET because the gm of bipolars is much higher. "The output swing will occur in either direction as rapidly as the internal carrier creation or recombination processes within the transistor, or the external circuit capacitances allow." "Zout = 1/gm" "For a bipolar with a gm of 35mS per ma of current, which is being operated at 1 ma., the expected output impedance will be 1/1*35 kilohms = 28.57 ohms. This is sufficiently low that the value of the emitter resistor has no practical effect on the output impedance." Jim

3/4/2000 5:01 PM

Jim

Re: no subject

same guru also told me that in his e-mail too. The output z of a follower is low for both positive and negative swings. Bipolar lower than FET because the gm of bipolars is much higher.

"The output swing will occur in either direction as rapidly as the internal carrier creation or recombination processes within the transistor, or the external circuit capacitances allow."

"Zout = 1/gm"

"For a bipolar with a gm of 35mS per ma of current, which is being operated at 1 ma., the expected output impedance will be 1/1*35 kilohms = 28.57 ohms. This is sufficiently low that the value of the emitter resistor has no practical effect on the output impedance."

Jim