From: Winfield Hill
Subject: Re: Limitations of the BC337
Date: 13 Jan 2003 05:02:22 -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
Ran a spice response plot of my circuit above. Showed gain of
16.0 flat to 3MHz, down 3dB at 10MHz. Gain = 3.88 at 40MHz
for our BC337 with 50-ohm source and load. That indicates an
f_T better than 155MHz for the spice part model at 20mA and 5V.