[sdiy] Single transistor Class A input/Output Impedance?

[Donald Tillman]

On Feb 21, 2014, at 12:21 PM, Justin Owen <juzowen at gmail.com> wrote:

> On this standard textbook circuit - what sets the input and output impedance? Is it R2 or R1 || R2?

(Heh-heh, the way you worded that is ironic.  A textbook circuit you say?)

The input impedance will be the parallel combination of R1, R2, and the resistive loading of the transistor's BE junction.

The output impedance is, roughly, RL.

> I've also seen versions (mainly for guitar pre-amp/boosters) with a Megohm R in parallel (in front of) with R2.

Probably on the left side of the cap, and that would be standard practice to keep the cap from collecting a charge.

  -- Don

--
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com
650 888-9632