From: Winfield Hill
Subject: Re: Limitations of the BC337
Date: 13 Jan 2003 05:35:33 -0800
Organization: Rowland Institute
X-Newsreader: Direct Read News 4.20
> John Woodgate opined thusly:
>> Paul Burridge wrote
>>> Perhaps if Virgin ever get around to fixing up
>>> their lousy service I might be able to post a schematic.
>> Use ASCII art. It's not that difficult. Use Courier font.
> Oh very well.... For those of you who are unable to resolve
> a net list (posted under another thread) here's my best attempt:
Very nice Paul, good first try! I removed some extra spaces,
tabs?, etc., whatever, to make it viewable with a fixed font.
> -------------------- 10v+
> | |
> 150k 150k
> | |______ 100n______Vout~
> | |
> | C/
> ___100n___|____B Q1
> | | E BC337
> | | \
> | 150k |_______
> Vs~ | | |
> | | 140k 100n
> | | | |
> Flippin' 'eck. I hope no one asks me to do that again!
OK, ran a spice plot of this. The low input capacitor value means
it's having difficulty with frequencies below 1.6kHz - it reaches
a gain of +45dB and is flat from 5 to 40kHz. It's down -3dB by
107kHz, and has no gain at 40MHz as you observed. That's because
you've got the BC337 running starved at Ic = 80uA and Vce = 0.76V,
and with a high 150k load (note my comments on the effect of Cob).
Note my post a few minutes ago showing a gain of about 4x for the
BC337 at 40MHz, using a circuit better suited for high frequencies.