From: Winfield Hill
Subject: Re: Limitations of the BC337
Date: 12 Jan 2003 08:16:48 -0800
Organization: Rowland Institute
X-Newsreader: Direct Read News 4.20
Paul Burridge wrote...
> John Jardine opined,
>> Incidentally ... What was your rough gain and source impedance?.
> Unity and zero respectively.
> Confused? Understandable. It's a Spice simulation. I was aiming to get
> a reasonable gain at the required 40Mhz, but there was zilch output.
The BC337 is a respectable and popular transistor. A web search
shows huge quantities available on distributors shelves at very
low prices, from at least 12 different semi manufacturers (e.g.,
Newark has 10179 available of ON Semi parts for 5 cents, qty 1k).
According to the Siemens data sheet, the BC337 has f_T over 100MHz
for collector currents from 7 to 170mA with Vce=5V, and an f_T of
180MHz at 50mA. ON semi's data sheet shows its Ccb capacitance is
only 5pF at 5V. So BC337 transistors can make a 40MHz amplifier,
especially if several are used. It's entirely a matter of your
specific circuit design. For example, this simple circuit biases
the BC337 near 20mA and 5V, and is intended for use with a 50-ohm
source and load. At 200kHz and below its voltage gain should be
about 35 to 40, if my back-of-the-envelope is working. It should
still have a gain of say 2 or so by 40MHz (a more complex circuit
could have a "flat" gain to 40MHz).
. | +----||--- out
. 3.3k |
. | C BC337
. | E
. 560 |
. | gnd
Tell us about your design, the collector current, load resistance,
the bias setup, emitter resistor and bypassing if any, etc., etc.
What spice software are you using? Post your BC337 model for us;
let's get to the bottom of this "zilch" business. :>)