I modified an astable multivibrator to send an alternating current across a load (square wave centered at 0V), given a DC power supply. The multivibrator is connected to to the load through an H-bridge and the multivibrator alternates which switches are on and off via transistors. The point is that the multivibrator saps out a certain amount of power and the rest is left to flow across the load. My problem is that if the resistance of the load is too small, square wave deteriorates. I am positive this is because the device not getting enough power because too much current is flowing across the load. I am not sure how to calculate the power consumption of an astable multivibrator. I know how to calculate power consumption of simple LRC circuits, but my background and experience in circuitry is limited to the electronics/circuits section of some introductory physics courses. Here is one of MANY links to the multivibrator my circuit is based on: http://upload.wikimedia.org/wikipedia/commons/6/6a/Transistor_Multivibrator.svg PS: What is the significance of R1 and R4 in this design--there was not a SINGLE article that discussed that!