From: Mike Monett
X-Mailer: Mozilla 2.02 (Win16; I)
Subject: Re: Amplifying stage with negative Vgain??
References: <email@example.com> <3DEF7AA3.firstname.lastname@example.org> <email@example.com>
Date: Fri, 06 Dec 2002 08:11:54 -0500
NNTP-Posting-Date: Fri, 06 Dec 2002 08:11:58 EST
Organization: Bell Sympatico
Paul Burridge wrote:
> On Thu, 05 Dec 2002 16:10:35 GMT, Fred Bloggs
> opined thusly:
> >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?
> My data book states that this device *does* come in varying pin-outs,
> so it was one of the first things I checked out. However, the specific
> device concerned is a BC337-16 which (when looked at from above with
> the flat side to the left) has (from top to bottom) C, B & E
> respectively. The DC voltage readings are (WRT GND) 12.5, 6.1 & 5.5v
> respectively. And these are pretty much the voltages anyone would
> expect, IMV
The readings are a bit off. If the supply is 12.5V, the base should be at
6.25V, and the Vbe drop should be closer to 0.7V, but that will depend on
the transistor type and ambient temperature. You might be using a VOM
instead of a DVM. This would drop the indicated base voltage a bit, but
the emitter follower would not be affected. Anyway, they are close enough
to say the transistor is working at DC.
You can check the transistor pinout by using your ohmmeter to measure the
resistance between all three leads. The one that shows a low resistance
(600 ohms to 1.2k) to the other two is the base. Now all you have to do
is identify the collector.
Connect the ohmmeter across the remaining two leads with the positive
lead going to the suspected collector. Wet your finger and place it
between the collector and the base. Repeat with the other lead. The one
that gives the lowest reading is the collector.
Or, hustle down to Radio Shack and get a DVM that can test transistors:)