Patent ID: 7362530

Claim:
A differential amplifier, comprising: (a) first and second bipolar transistors connected as an input differential pair with their emitters connected together and to a current source; (b) first and second loads for said first and second transistor collectors, respectively, and a differential output at said first and second loads; and (c) third and fourth transistors, where said third transistor connects between said second transistor collector and said second load and said fourth transistor connects between said first transistor collector and said first load, and where a base of said third transistor couples to a base of said first transistor and a base of said fourth transistor couples to a base of said second transistor; (d) whereby input resistance of said differential amplifier is increased due to said coupled first and third bases and said coupled second and fourth bases, wherein said first and third bases are connected by a first diode and said second and fourth bases are connected by a second diode; whereby the direction of differential-signal induced base current at said first transistor is opposite the direction of differential-signal induced base current at said third transistor and thereby providing an increased differential-signal input resistance for said differential amplifier.