From: John Woodgate
Subject: Re: Transistor amplifiers v. frequency in SPICE
Date: Sun, 12 Jan 2003 22:33:56 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Sun, 12 Jan 2003 22:59:14 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Winfield Hill
wrote (in ) about 'Transistor amplifiers v.
frequency in SPICE', on Sun, 12 Jan 2003:
>. +24V | 1nF
>. | +----||--- out
>. 150k |
>. 1nF | C BC337
>. --||--+---B 2n2222
>. | E
>. 150k |
>. | +-----,
>. gnd | |
>. 140k 1nF
>. | |
>. gnd gnd
> Another problem with your circuit (did I get it right?),
I couldn't make anything else out of it. But the OP claimed 1 V out for
2 mV in at low frequencies. At 80 uA, re = 490 ohms, so he's trying to
get a gain of 300 out of one stage, assuming that the load impedance is
high compared with 150 kohms, which it won't be, of course.
> have a very low collector-emitter voltage, nearly saturated.
> Better check it. Assuming beta = 50, I calculate VE ~= 11V,
> 78uA emitter current, collector IC = 76.5uA, so VC = 12.5V,
> for Vce = 1.5 volts! No wonder you see distortion! :>)
That would be OK if the input voltage were small enough, of course. But
I'm puzzled by this high frequency, high-impedance source. That doesn't
sound realistic, either.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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