From: Fred Bloggs
User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0
X-Accept-Language: en-us, en
Subject: Re: Amplifying stage with negative Vgain??
Date: Thu, 05 Dec 2002 16:10:35 GMT
NNTP-Posting-Date: Thu, 05 Dec 2002 08:10:35 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
Paul Burridge wrote:
> On Wed, 4 Dec 2002 10:28:14 -0000, "Kevin Aylward"
> opined thusly:
>>What is your exact configuration, i.e. load impedance, source impedance,
>>operating current. Is this a sim or real life?
> I don't see impedance coming into it, quite honestly. The input signal
> is still a healthy 8v directly on the base of the buffer device's
> transistor. On the emitter pin, however, it's just 2v.
> The circuit is a dead simple single stage C/C amp. R1 and R2 (both 3k)
> split 12v supply in half to bias the base of Q1 at 6v; there's no
> collector resistor (straight to Vcc) and RE is 1,080 ohms. The input
> and output coupling caps are both 1n. There was no load when the
> measurement was made - other than my scope of course.
> This is *not* a simulation as you may well have gathered by now.
If the BC337 pinout is such that you have connected E to the input
junction of the 3k's, B to 12V, and C to the 1080 output resistor, then
you end up with a configuration that gets 2Vp-p across that 1080 for
8Vp-p at the input. You have almost certainly done something like this.
You can figure this out if you measure the quiescent DC voltages at the
three nodes- what are they?