Dave Jones from the EEVBlog does a very good short introduction to dBs. http://www.eevblog.com/2009/12/13/eevblog-49-decibels-dbs-for-engineers-a-tutorial/ htt

Dave Jones from the EEVBlog does a very good short introduction to dBs. http://www.eevblog.com/2009/12/13/eevblog-49-decibels-dbs-for-engineers-a-tutorial/ http://www.eevblog.com/2009/12/13/eevblog-49-decibels-dbs-fo... dBs are always relational or relative in nature. The relationship is between two signals or one signal and an agreed reference. If the relationship is between a signal and an agreed reference, the convention is to append an identifier to the "dB" unit, e.g. dBV or dBm. 0dBV is 1V since the agreed reference for dBV is 1V. Hope this helps.