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Path: ...!eternal-september.org!feeder2.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: chrisq <devzero@nospam.com> Newsgroups: sci.electronics.design Subject: Re: Curve Tracers Date: Fri, 22 Nov 2024 00:37:37 +0000 Organization: A noiseless patient Spider Lines: 29 Message-ID: <vhojoh$s7ot$1@dont-email.me> References: <vhkhcg$2ip8$2@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Fri, 22 Nov 2024 01:37:37 +0100 (CET) Injection-Info: dont-email.me; posting-host="c430eb6b30f3047c46e778c31c71d755"; logging-data="925469"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18I1PCInTgrhNUMj4/74s3d" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:55k/oqPHjqvAzjkJoNPGOK8d238= In-Reply-To: <vhkhcg$2ip8$2@dont-email.me> Content-Language: en-US Bytes: 2248 On 11/20/24 11:32, Cursitor Doom wrote: > Gentlemen, > > Curve tracers reveal useful info about the dynamic characteristics of > semiconductors and make designing for same much more predictable and > dependable than relying on spice models and simulation alone. But they're > typically rare beasts and expensive to come by and boat anchor varieties > are seriously heavy and bulky. > I think therefore that a curve tracer would make an excellent project, > using the X&Y inputs of a scope as the display. Has anyone here attempted > this? I'd be interested to know what the main challenges are likely to be. > > -CD It's not too difficult to build a low power ct. We built one in school decades ago, using a diode pump and clock, to generate the stair step base drive. IIrc, we used half wave rectified ac for the collector sweep. Not so easy to build an accurate system, especially for testing power devices, which typically need high voltage and current. Here, an old Fairchild 6200B, none working from Ebay, gets regular use, both go / no go and for matching devices. That dates back to the late 1960s, and uses a four stage binary counter, with 1,2,4,8 resistor network d to a, to generate the stairstep. A small variac drives the collector sweep. Chris