Re: diode-connected transistors

From: Terry Given (my_name_at_ieee.org)
Date: 11/16/04 

Date: Wed, 17 Nov 2004 11:12:45 +1300

John Larkin wrote:

> On Wed, 17 Nov 2004 06:11:02 +1300, Terry Given <my_name@ieee.org>
> wrote:
>
>
>>I often use diode-connected npn and pnp transistors. Sometimes I use the
>> base-emitter junction reverse-breakdown as a (somewhat dodgy) zener,
>>sometimes I use them as diodes. When used as a diode, I can either use
>>the c-b junction (b shorted to e) or the b-e junction (b shorted to c).
>>
>>Here are my questions:
>>1. Which configuration has the lowest capacitance ?
>>2. which configuration has the lowest leakage current?
>>
>>In a more general sense, what are the pros and cons of either
>>connection? Using say bc547 and bc557 transistors.
>>
>>Cheers
>>Terry
>
>
>
> Some NPNs make superb reference zeners if operated as a zener, C-E
> with the base open. The tc of the forward-biased cb junction cancels
> the tc of the zenering be junction; this works right at about 6.2
> volts overall.
>
> John

Hi John,

Thanks, I'll try that. Care to elaborate on "some" ?

Thanks,
Terry

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