darlington/mosfet in emittor follower / headphone amp

[svokke]

lHow did you measure input impedance of transistor of 800 ohms?
This is very low, are you sure you did it correctly?
Maybe use a transistor of higher beta like 2sa4793
regards

I measured the input resistance by putting a resistor between the base of the transistor and the opamp. Then measuring the voltage across the resistor. Then you have the base current. Then measure the voltage at the base. Base voltage divided by the base current= base input resistance.

The only difference compared to the first image, that I use resistors between the base and the emitter of the transistors. 4.7kohms for the BC, and 220ohms for the MJE.

Why is this done and how did you calculate the values?

I still have a lot to learn, that's one of my reasons why I like DIY

[ilimzn]

Originally posted by Gasho
G. ilimzn , vidim da ste iz Zagreba , pa me zanima možemo li nekako kontaktirati , barem preko maila?

Ilimzn_at_hotmail_dot_com ali rijetko provjeravam pa malo strpljenja. Alternativno, ilimzn na audiokarma.org - tamo je dopusteno slanje 'private messages'.

Sorry for hogging the thread folks, just a quick correspondence with a guy from where I live