Unwanted oscillations

Jul 19, 2003 2 Replies
C

I've got a simple circuit that uses a BC337 NPN transistor to switch a DC buzzer on and off.. It's set up as a classic common emitter switch eg The Buzzer is in the collector circuit and the base is driven by a micro via a



1K resistor. The problem is the pesky thing oscillates. I didn't do the PCB layout and I suspect that the cause is some inductance in the emiter trace? Any ideas for a cure?

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C

Thanks for the reply. I'm using a small 12V Peizo buzzer.

The data sheet is here...

formatting link

... but it's next to useless - no data on impedence etc.

If I apply a Mk1 finger between base and collector the oscillations become audible - but I'm not sure that means a lot.

Think I'll try decoupling the base first.

Colin

DC

The

a

collector

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W

In article , snipped-for-privacy@comcast.net mentioned...

More to the point, do you have a diode across the buzzer coil, cathode to positive? If not, then the peak voltage may exceed the transistors max rating.

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