Hi All,
I'm trying to simulate a circa 1960's circuit that creates a noise based sound effect (torpedo launch "Swoosh"). The circuit uses a PNP transistor with an open collector. I assume this transistor generates noise which is then conditioned by the rest of the circuit. LTspice complains the the node is floating and will not continue with the simulation. Is there a way to tell LTspice to ignore this floating node? See cicuit below:

Thanks in advance,
Scott

 

Add a resistor to the "OUT" output, for example 47 kΩ. The second pin of the resistor is connected to ground GND. Then there will be no floating node.

 

Connect a very high value resistor from the collector of Q1 to its emitter. I would use something like 100Meg. (You must spell out "Meg" since 100M would be interpreted as 100 mil ohms.)

 

Add a resistor to the "OUT" output, for example 47 kΩ. The second pin of the resistor is connected to ground GND. Then there will be no floating node.

Probably the best idea - LTspice goes on strike if there's loose ends.

I'm guessing that's a germanium transistor used as a noise generator - there were germanium Zeners, but not abundantly.

 

Probably the best idea - LTspice goes on strike if there's loose ends.

I'm guessing that's a germanium transistor used as a noise generator - there were germanium Zeners, but not abundantly.

My suggestion of adding a high value resistor to the collector of Q1 may not be valid. I just did a quick test and LTspice did _not_ complain about a floating collector of a transistor.

 

See
Noise Gen. with changed on-hand transistors
https://forum.allaboutcircuits.com/...nged-on-hand-transistors.137813/#post-1155674
Specify the types (brands) of transistors. And the breakdown voltage of the emitter junction of the first transistor. I will help to select similar germanium transistors and their spice models.

 

Add a resistor to the "OUT" output, for example 47 kΩ. The second pin of the resistor is connected to ground GND. Then there will be no floating node.

How would that solve a problem with the collector of Q1 floating?

 

If your circuit relies on a component acting as a noise generator, then a simple LTSpice transient simulation won't do much for you.

You need to model the noise source as a suitable voltage/current source and use an appropriate math function to get the desired signal properties.

 

See