T&L Publications

Hello, all
The c is a commonly used IC designed to produce a variety of output waveforms with the addition of an external RC network
For this little circuit, I'm using an Oscillator (parameter source: https://www.apogeeweb.net/circuitry/ne5 ... tions.html. Everything is well in the beginning. But it came out faulty after finishing.
With the collector unconnected the emitter (pin1 ) still sinks (20mA) and sources (30mA) current, when applying a square wave input. I measured mean dc amperage to either rail, so the max is higher. I cannot explain this behavior.
Doing the current measurement on the collector (pin 4) with an unconnected emitter I get 20mA when sinking, and none when sourcing. But not following the input signal.

Are there any suggestions for this? Many thanks.

??? pin 1 of the 555 is not an emitter, it is common supply pin, and should not be open.

Do you mean when collector of the transistor is open there is 20mA through the emitter of the NPN transistor?

When the output of 555 (pin 3) is high, the base-emitter of the transistor is forward biased, so there will be current. 1K * 20mA = 20V. Max supply for a 555 is 18V. If you really mean pin 1 open, that's not a proper hook-up.

Pin 4 of 555 is reset not (pull to common to reset the 555), you are not seeing 20 or 30mA there unless the 555 is destroyed.

The right schematic shows current (green arrow) through emitter of a PNP transistor. So what emitter is open?

Cheers,