J
Jamie
- Jan 1, 1970
- 0
Hey, thats a good idea, dual package logic transistor..Spehro said:On 17/01/2011 2:41 AM, John Fields wrote:
On Mon, 17 Jan 2011 01:51:47 +1100, Sylvia Else
On 17/01/2011 12:20 AM, Sylvia Else wrote:I would add that I wouldn't want to use this approach in a circuit
intended for mass production. A combination of adverse IC output
characteristic, resistor value and transistor variation would mean it
was asking for trouble.
But as a one off...?
---
Maybe, but still kinda scary unless you could pin everything down.
He could get more leeway by putting a diode between the emitter and 18v,
and the cost of reducing the voltage across his load, which is now
revealed to be a piezo beeper.
However, that pushes up the component count again, and space was stated
to be an issue.
---
Indeed; that's why I'll stick with my original solution of an N MOSFET
(with, conceivably, no gate resistor) being driven by the 4013's Q
output or an NPN with a gate resistor being driven from the same
point.
That is, if Q isn't being loaded so heavily by what's already there
that my scheme won't work.
_
If it won't, and he's forced to use Q, then I'd bite the real-estate
bullet and use two NPN's, like this:
+18
+18 |
| [BUZZER]
[10k] |
| C
+--[10k]--B 2N3904
| E
_ C |
Q>--[10k]--B 2N3904 GND
E
|
GND
No Zeners, no tricks, no marginal operation, just a rock-solid switch.
You don't need the 10K between C and B of the 2N3904s.
He could also use one of these, plus one resistor:
http://www.onsemi.com/pub_link/Collateral/MUN5211DW1T1-D.PDF