  The conventional two transistor astable multivibrator has been modified to
produce better waveform which are more steeply rising and falling than those
from the conventional astable. The improvement in the waveform is achieved by
using a diode pair in each collector branch of the transistors. This restricts
the direction of current flow for the charging and discharging of the timing
capacitors. This article also derives the time period of oscillations for the
modified circuit and discusses the limits on source and sink currents at the
transistor collectors.
