[sdiy] JP8 Gate circuit issue

[Phil Macphail]

I think you're right Tom, but a totem-pole output can still drive the
circuit if you leave the resistor in-circuit.

Phil.

On 31/10/2013 23:15, "Tom Wiltshire" <tom at electricdruid.net> wrote:

>My guess is that it was intended to be driven by an open-collector
>output. E.g. by another transistor that looks much like the one you've
>got. That'd explain why there's R127, a pull-up, and it'd also explain
>why the circuit is inverting, since the open-collector output would be
>high when not switched on with just the pull-up attached.
>
>To modify it for a 0-5V input, just take R127 out. If it doesn't switch
>on properly, reduce R128.
>
>HTH,
>Tom
>
>On 31 Oct 2013, at 19:31, Jack Jackson <jackdamery at hotmail.co.uk> wrote:
>
>> Hey all, I'm trying to get this gate circuit from the JP8 working. As
>>far as I can tell you should apply 5v logic signal to the base of the
>>transistor and it should output 15v positive gate. I can't get any
>>change from it. I'm using correct resistor values, and a 2N3904 for the
>>NPN. Any ideas?
>> 
>> http://flic.kr/p/h9o13k 		 	   		
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