555 Output Characteristics

Thread Starter

Wendy

Joined Mar 24, 2008
23,415
SgtWookie and I had a discussion about 555 output and how much they can drive. I've started some circuits to test the concept. The first one kind establishes the basics.



The voltage was exactly 4.500, the output was 2.744VDC. This meant the circuit was drawing around 196ma give or take a bit.

I think we met the basic specs, though the voltage drop was a bit high.

I'm going to redesign my current source sink a bit.
 

Attachments

SgtWookie

Joined Jul 17, 2007
22,230
Bill,
Why not use an LM317 as a current sink? 6.25 Ohms from OUT to ADJ (1/2 Watt) should just about get you there; try a 9.1 Ohm and a 20 Ohm resistor in parallel. Then you can determine the voltage drop from the 555 under minimal load and 200mA load conditions.
 

Thread Starter

Wendy

Joined Mar 24, 2008
23,415
To use a 555 at 4.5VDC means it will below the minimum thresh hold insertion drop for a LM317. The first experiment was quick and dirty, and let me know I wouldn't be wasting my time doing more. I'm going to set it aside for a little bit, then get back to it.

I also have several different makes of 555s in my kits. The first was a KIA555.

**********************

Here is the type of regulators I'm thinking of using...

 

Attachments

Top