Most of us are very familiar with the Widlar current source which uses a resistor in series with a diode connected bipolar to act as a source for a current. It is probably the most popular current source in existence. However, this source does have its problems such as variations with resistance,
and the low input resistance of the bipolar. There is another lesser known current source known as a “peaking” current source that at times can be used with advantages beyond those offered by the time honored Widlar source. It is also useful when the supply voltages are low. A white paper on this source is available now by courtesy of the Techteam at Signal Processing Group Inc. For interested readers it is located at http://www.signalpro.biz/> engineer’s corner.